I personally have the SuperChips Flashpaq and love it. I got it for a couple of reasons. The price was right (I picked it from another member looking to get in to a Diablo) and it's all I need. The Flashpaq comes with 3 different canned tunes, Mileage, Towing and Performance. Plus I was able to calibrate my speedo to compensate for my bigger tires. Made the speedo dead on.
Lots of threads and info on here about all the different tuners. As far as the best place to get one, I'd shop around or keep an eye here or on craigs list or kijiji.
Life is hard... It's harder if you're stupid!
Today is a good day to be a RAM owner!