I use the Optima series, mounted sideways.
I've logged about 9,000 miles with this set-up, including some hard driving at Sears Point. I also have a lot of electronics to run (DVD, Stereo, Rear Wide-Angle Camera, etc.) at car shows, for up to 6 hours.
I've never hard a problem with it. At least it works for me. You can see this battery at "www.ViperProject.com", "engine" section. They sell this battery almost everywhere...