Don't know if you can read it, but what I've tried to do here is import a spread sheet from Excel (as a jpeg) that gives the full list of all the parts I used on the new drive train and the costs. The total cost is around $535. That's compared to $1k or so for the JAG drives, or about the same for the Senna drive system. I was able to cut a lot of the costs by getting all the gears, chains, and other stuff for a fraction of the price at The Surplus Center. A scooter motor set up will cost you less--you could probably get it all done for under $200 if you had the tools and the determination to do it all yourself. Email me for more details if you need them.
I've also been looking at some of the documentation for the Sabertooth 2 x 25 speed controller I'm using from Dimension Engineering. It looks like you can get different sorts of response curves with different dip switch settings. So I'm going to tinker with those a bit and see if I can get those high torque motors to start up and stop a bit more gently. Anyone have any experience setting that up with NPC motors and the Sabertooth?