Have a look at Roger Plants website, http://www.bigcheeserobot.comhttp://www.bigcheeserobot.com - he has combined gearboxes and axles and motors to fit them, and suitable speed controllers.

2 axles: 30 gbp
2 reliance motors: 50gbp
2 Curtis 1208C speed controllers: 100gbp
Total 180 gbp for all the power transmission components you need, plus a bit for postage and packing.

This will not give you as much pushing power as Storm II but at this stage I wouldnt worry about it. It will almost certainly be more power than your wheels can put down onto the floor. You say you are more interested in innovation than winning, which is a commendable attitude, and you shouldnt worry about being underrated in terms of power. Reliability is more difficult to quantify and is, in general, better with tried and trusted components like these rather than bleeding-edge technology.

I would advise against building your own speed controllers. I tried this, and it was a very interesting project, but there were a lot of difficulties and I gave up once I realised I could get the Curtis controllers for 50 pounds. You may find that a lot of your existing knowledge of circuits doesnt hold when youre into hundreds of amps. Of course, you may know enough about this field to make a good job of it. Mine lasted about 30 seconds in its first proper fight, which was a severe disappointment considering they let down the time Id put into the rest of the robot.

Control electronics are much easier (from my point of view) and theres still room for quite a bit of creativity there if you just treat the speed controllers as power output stages. Just make dead certain it fails safe!

Best of luck.