if you belong to Sam's club - they have Duracell AGM - for the price they sell them for its worth joining just to get the batteries
if going lithium - contact drewcraft.com for ionics - usually a discount if you contact him thru Bass Boat central. I changed my trolling motor batteries to ionics and couldn't be happier
I've had the Sam's Duracell AGM 31 before and for the low price it was a good battery. I think I got about 3 1/2 years out of it before it wouldn't hold a charge for very long. I decided to spend more and got an Odyssey Extreme 31M PC2150 based upon a recommendation from a friend who has run them for years. I haven't been disappointed. It is very sturdy, well built, it has as much amps as you can get in a 31M size and I believe when used as a cranking battery mine came with a full 5 year non pro rated warranty (may only be 4 now, not sure). It was expensive, they cost around $580.00 but it has the power! For trolling motor batteries I tried Interstates with mixed results. For me the best value is just the Walmart Dual purpose Everstart 29DC. If you can get the Maxx version you get a longer warranty but I'm not real sure there is any real difference in construction between the regular 29DC marine and the Maxx version. It seems like I get 4 or 5 years from the Everstarts and that is by taking care of them (recharge right after use and keep the fluid level where it is supposed to be).
if just wanting a great lead acid - the big 31 commercial Napa is a great starting battery - mines going on four years old. if you want more details let me know and i will look up - its about $200
Get the 125 amp hour ionic for your cranking. Had mine for 2 and half years and have had 0 issues on my 200 proxs. I run two 12" screens, one 10" screen, Active Target 1 box, SS3D box, sonic hub, and all accessories with one battery.