Here is a photo of my current motor with my old battery pack (30 NiMH "D" cell flashlight batteries... if you want to try it your self I'll sell them to you cheap, but you might be disappointed), it is the mid speed
crystalyte phoenix motor all of their motors are designed for 72 volts but their kits come in 36, 48 and 72 volt kits, allowing you to save money on controllers and batteries.
I'm still pleased with mine, although near the top end of the price range it is basically a 1400 watt motor at 36 volts and at 72 volts can put out 2800 watts or more or nearly 4 horse power.
A friend with the phoenix racer motor just had his foxx power lithium battery show up, 20 amp hours at 48 volts weighing about 30 pounds, it will be fun to see what it can do.
of course you should always check local laws, Wisconsin is amazing, 30mph using the power device, must have pedals, user must have a learners permit or higher license.
California I think has a 20mph speed limit, allot of kits market towards that state and put low quality controllers in that top out at 20mph because of that.