US Battery is the manufacturer of my current bank.
I have 750w solar panels, in addition to 1x 90A and 1 x 140A alternator, so I normally get my bank back up to 100% each en if we don't run the engines.
Ah.
Well, I generally like AGMs, but their advantages often cost a lot compared to flooded batteries. No service, great! Reduced off-gassing, great! Faster charging, great -- if you can do it! Alternative installation orientation, maybe useful for some but we haven't needed that. $$$ or $$$$$ depending on brand, not as great.
I dunno that just any ol' brand of "deep cycle" 12V AGMs is really going to be a deep cycle battery. (You could compare predicted cycle life for each option...)
Given your existing 6V/880-Ah configuration (4 pairs of GC2, yes?), and assuming you can easily service the things... I think I'd be inclined to stay with your proven set-up. You could change those to AGMs (Lifeline or at least one other 6V AGM maker), but unless service is a pain, can't say as it'd be worth the money. Or if you want even more capacity, maybe L16s would fit in the same space (heavy, though).
Can't say as I'd want to lift any 4Ds or especially 8Ds, so largest we've used are Group 31s... and they were heavy enough. If those 174-Ah things are in the 4D/8D category, I'd put that weight thing down as one of the downsides even though I recognize you said up front that it wouldn't be a problem for you.
-Chris
