If your really serious about deep cycle batteries have a look at these. Give them a few years and they should be quite a bit cheaper. We just installed some 12V 130AH ones into an educational trailer that goes out to schools and teaches students all about solar power, battery power, mains power etc etc etc.

http://www.ev-power.com.au/-EV-Power...atteries-.html

PS, this is not a plug for the company or the batteries. Just thought you might be interested in what out there.