Do you have a Costco in your area? They have great prices and warranties for batteries. I now use the same battery model in my tractor, Ford Powerstroke F350, and V10 Excursion. 850CCA/1000CA, 100 month warranty, and about $100.
Another great option if you don't have a Costco, see if you have an Interstate Batteries in your area. I have found their prices to be very good and I have had great luck with their batteries lasting.
One key to keeping a battery for long periods of time for me, is to keep it hooked up to a Battery Tender or Battery Minder when it is parked.