I have group 31 Deka Absorbed Glass Mat (AGM) Batteries, best batteries I have owned. Period. I bought mine through my local marine store. The AGM batteries are a bit more expensive than it's traditional lead acid counter part, but in my opiniopn, worth the extra $$ I think I paid around $230 each for the AGM. I run my 2500 watt stereo for 8 hrs on one. I just added a second one to extend to 16 hrs. They are heavy @ 75 lbs each....

I just bought a group 27 Interstate deep cycle battery from batteries plus. This is my 3rd interstate battery. I have never had a problem, and consumer reports always ranks them high.