you dont need 4, Alpha and Omega run well on 2 24v golds, they both have a similar speed/torque but ones 2wd and Omega is 4wd. Both using 15amp cpu electronize, although relays would need to be replaced after about a year (saying that they did run in alot of fights).

You could look at overvolting the 12v golds, stiff breeze does this and run very well on 6wd. But you will need some good speedos, modified 30amp electronize might do it, but i would be looking at something bigger.

For batteries look here:
http://www.modelpower.co.ukwww.modelpower.co.uk
http://www.overlander.co.ukwww.overlander.co.uk

Alpha use to run 3Ah botpacks but due to weight now runs 2.4ah, alot of people use the 2.4ah sanyo cells.

http://www.blazerbotics.co.ukwww.blazerbotics.co.uk