650rpm on 4" wheels is OK, that is about 7.7mph. The Honey Badger 2.2 used 4.33 inch wheels with a motor/gearbox giving about 844rpm at 19.8v meaning about 11mph and if you watch some of the videos of it at Manchester 2018, that was petty fast.

If you wanted 9mph, you'd want about 770rpm for example which I imagine is achievable with the motors you are looking at by overvolting slightly.