If you're on a budget, want that many wheels, and want a real durable wheel (much more so than the banebots), I'd say Colsons are the way to go.
Robot Marketplace has a nice selection.
With that many wheels, I'd go with the 7/8" or 1-1/4" wide, and 3-5" OD due to cost and weight. You don't really need to go to the wider and heavier wheels.