The cost here seems to be the biggest issue; even if you get some big, powerful, motors on the cheap, the controllers sure won't be.
I don't have any links on hand, but there are many "surplus" sites that may have motors to suit your application. A lot have gearboxes already on them for various applications, so I think getting lucky and finding a good motor/gearbox combination would be your best bet.
Robot Marketplace has a lot of random motors people have used to power heavyweight (320 lb) combat robots, so something there probably is powerful enough to power your snowblower; especially since you'll be gearing down substantially. The problem is, for the big boys you need some serious cash; and most are just motors, no gearboxes.
I'd say if you have work with a team, see if you can find a way to do it with small CIMs. Crunch the numbers and do some tests to see how much power you really need to drive it, and see if a pair (any more than 2 and the implementation get's clunky fast, as you can no longer use a COTS gearbox) geared real low will cut it.