check out the scorpion XL on
http://www.robotpower.comwww.robotpower.com
I sell these in the UK so drop me an email if you like the look of them.

see also
http://www.technobots.co.ukwww.technobots.co.uk
for electronize and other suitable controllers
anything 18v/15A capable should be fine, as you wont be drawing too many amps until you start overvolting the motors.

Between technobots and I, you have lots of very good options. Drop me, or technobots an e-mail if you need more info about specific controllers