The Hi-Grip wheels that come with the kit frame are pretty decent wheels for a drive. If you're looking for similar wheels that may add some more traction, I would personally suggest these:
http://www.andymark.com/Plaction-s/103.htm or these:
http://www.andymark.com/Performance-s/101.htm
I personally like using colsons in a drivetrain (
http://www.vexrobotics.com/vexpro/mo...nperforma.html) but I'm not sure how easy/possible it is to put them in the kit frame.
Edit: the treaded wheels I posted above require the ability to rivet it to the wheel, so I wouldn't buy them if you can't rivet.