W.B.
I would recommend two marine deep cycle AGM batteries. These batteries are made for starting power and deep discharging the best of both worlds. Because they are AGM, the discharge rate when not in use is extremely low compared to other battery types.
For a specific brand, you can't beat this Duracell Marine AGM battery for the price.
http://www.samsclub.com/sams/shop/pr...navAction=push
Compare the specs to any other battery out there and you will see what I mean.
Dan