Thanks again everybody -- very helpful.
Cam, I am inclined to try that Lifeline GPL 1400T that Paul linked to. It prices out at $180 (BD Batteries - delivered) which is steep for a battery of this size (I paid about that price for our Grp 31s albeit 5 years ago -- looks like prices have gone way up). But given their track record on our boat, I know Lifelines represent good value.
I had toyed with the idea of doing some R&D with an Odyssey battery like the PC1200 ( PC 1200 Deepcycle Odyssey Battery, Marine Heavy Duty Battery, Diesel, Trolling Motors - Odyssey Drycell Batteries
), but I haven't found a price for them yet. I expect it will be pricier than the Lifeline, and I really need to cap out the costs of this project....