Hi Eastsounder,
I think you are probably right about the transducer. So possibly no point in getting the bundle, because the RV-100 transducer is typically over $300. I just grabbed that bundle to illustrate.
But basically you can plug any "Raymarine flavored" transducer into the "RV" Axiom. For example (sorry, it's another transom mount) I had an Airmar P-66 transducer with my old Garmin that I really liked. It's just a basic one, with depth, paddlewheel speed through the water, and water temp. Nothing fancy. I did have to buy another P-66 with "Raymarine flavored cord end" but other than that it mounted right up. Again, sorry, I know this doesn't specifically help because you don't want a transom mounted transducer.
More on the Raymarine stuff below, but on the depth sounder:
Another possible "cheapish now, but still useful later" option is something like a simple Hawkeye depth sounder (for that I have an inside-the-hull glue-down transducer, which is great if you have an area of your hull that is not cored but is solid fiberglass). But they have other transducers. So this just has a ~2" round display, and just shows a number (feet). Super basic.
I have a Hawkeye for three reasons:
1) It draws very little power so I can leave it on overnight without the whole "system" of everything else being on.
2) Because it is glued inside the hull, and because my other transducers are transom mount, it's the one that cannot get knocked off or damaged.
3) It is a stand alone and only needs DC power (and not much). No NMEA, no network, no plotter required.
I have the Hawkeye Depthtrax 2B just as an example.
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Back to the Raymarine Axiom (+).
Note that if you are getting a non-plus Axiom, then they used to only have the sounder in the "RV" version. It looks like with the + series they all have the sounder. They also seem to be only bundling Lighthouse charts now (tho I see a few still with Navionics charts for sale (has "NAG" in the part number) and of course you can buy them separately. I want to say they were around $150?
But so if you are buying a "plain" 7, 9, or 12 (not +) then you want to make sure you have the RV model so you have the sounder. This kind of makes sense as previously each MFD had like 9 different sub-models with all the possible combinations. Must have been a nightmare to stock!
I have two (plain) Axioms and I did buy both as RV models. Just so that if one went awry I could still plug my depth sounders into the other one (ha ha, can you tell I had a trip compromised when a lone depth sounder quit working?).
But after that I only got what I needed. In my case I bought the first one with Navionics charts included, and the second one had no charts included. So I bought the Lighthouse charts separately. I like having both to compare and contrast.
The first one also happened to include a transom mount RV-100 transducer, but only because it was bundled and so essentially free. I rarely use that one (prefer my old P-66).
With the + series the resolution and viewing angles got better, they went to an IPS screen, and they got more hp under the hood. But for example I do see a "plain" Axiom 9 on clearance at West Marine for $750 (no sounder module). It would network with any + models later on. I have one "plain" Axiom 9. I upgraded to a nicer 12 (old eyes!) but I still find the 9 quite useful. It of course shares everything (charts, radar, depth display) with the newer MFD. One feature I like is that you can set up one screen so it's just a gigantic depth number. I can see that from the cockpit which is handy (you can set up a bunch of "set" screens that you use often).
BTW, ignore the "Element" series. These are really stand alones in that they won't network with eg radar. So I don't think you'd want one of those.
There is also a Pro series of Axioms. These have the control pad on the right side (so you have touch screen and buttons/knob), and I think also include a fancier sounder module (like for serious anglers; not something an average cruiser would need).
I kind of wanted that button/knob panel but didn't really have room for it (makes the units wider) and the "Pro" model was quite a bit more expensive. Then I found out they make that same button pad as a stand-alone. You can plug it in to the unit and then put it wherever you want (like say in the arm of your helm chair).
So I decided ok, fine, I'll get the regular Axiom (which is now the "Plus" series), and if I miss that button panel I'll get a stand alone. Turns out I guess I have modernized to the point where I don't miss the button panel (but you might want it).
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Have a look at these:
1) Axiom 9+ with sounder module and Navionics charts (indicated by "NAG" in the part number), free shipping $1299
The Raymarine AXIOM+ 9 with Navionics Plus Mapping is a great choice for your boat or yacht. Bright touch and Button Controlled display, get yours at The GPS Store.
www.thegpsstore.com
2) Raymarine Quantum2 radar with 10 meter cable (they do have a variation with a 15 meter cable), free shipping $2400
Raymarine Quantum 2 Q24D Doppler 18" Radar with Target tracking. Shows targets as they move towards or away from your vessel.. Available now at The GPS Store
www.thegpsstore.com
So the above is $3700. Navionics is maybe worth $100 over the Lighthouse charts that were in the other bundle from my previous post with the transducer you don't need. (But if you are an ebayer....?)
3) Bundle with Axiom 9+ with Lighthouse charts and Quantum2 radar with 10 meter cable (then you could buy Navionics charts stand-alone). Free shipping $3399
The GPS Store, Inc. Official Site - The Worlds Favorite Source for Marine Electronics, Garmin GPS units, Furuno, Lowrance, Raymarine & Accessories.
www.thegpsstore.com
There are no huge steals usually as prices are somewhat set. But sometimes you can find a bundle or a clearance item. Even at "retail" these are all well under $5,000. If you can do even basic reading of direcations, fishing cables, and plugging things in, then you can install yourself.
Last note on the Radar: The current 18" radome model is the Quantum 2. It has only one part number as far as the basic unit (there are variations in included cable length), and that is Q24D. It can connect by wifi or hard-wired (in terms of the data part).
There is also a Quantum (no "2" so essentially it's the "1" but it had no suffix). This is the previous model so should be less expensive. It had two part numbers: One was wi-fi only (for the data) and one was wi-fi or hard-wired. On the one hand, the Quantum "1" will work with older MFD's (A-series, etc.). But you don't need that. The Quantum 2 adds Doppler, which is nice. It shows targets coming toward you in red; going away from you in green. But if you found a screaming deal on a Quantum 1, it's still a Quantum radar.
BTW, if I sound like I have stock in Raymarine..... I don't. I just figure something like this helps to amortize the hundred hours of time I spent figuring it all out for my setup

I'm sure similar concepts exist for the other brands. And except for probably they all have something akin to the "Element" which is a bottom model and NOT something you can network, they probably all have similar features.
PS: On the autopilot. Do you have a hydraulic steering ram? If so, then the sizing goes by the volume of that steering ram (like 9 cubic inches or whatever). That's what determines which size of AP package you would go with, and that also sets up the pump size. EG I have about a 9 cubic inch ram, and that put me into a Type 1 AP pump and, with Raymarine, a EV-150 autopilot.
The EV-150 with a pump is now $1699 (GPS Store). When I bought mine there was a "core pack" which was the same thing for a little less money without the pump. The EV 200 is (of course) bigger and so will be more.
When you get the autopilot you also get (in the box) a separate control head (tho you can control it via the MFD, the separate control head is super nice as it has a knob that is essentially a miniature steering wheel - much nicer IMO than punching buttons only), a brain box, a sensor core, and some NMEA cabling (and maybe a pump, depending). That sensor core sends good information to the plotter that is useful for things other than the AP.