[EricH]

As a point of comparison, a couple years back my Lunabotics team used BaneBots RS-775-18 motors (running at 12V, and 1 for each of our 4 wheels), all running through a BaneBots P60 gearbox (I want to say 64:1 or 256:1)--and had one of the faster Lunabots if we kept our speed controllers alive.

Which brings up John's 2nd "extra" post. We had something like 20A (or 10A, in some cases!) fuses on the robot, one per wheel, and never blew one. OTOH, we rarely moved on the regolith because our speed controllers couldn't take the current, and shut down to prevent frying--and didn't restart until the robot did. A change in speed controllers--to something we could change the safety settings on () resulted in a lot of motion until we put ourselves in a sticky situation and couldn't get out... without frying speed controllers.

Plan for pushing, as John points out--you'll need it.