My first "e" was a 36V, 350w Dillenger kit on a rigid MTB, and it was great fun on and off road. The power built gradually and the front end never spun the tire. The same can't be said about my latest conversion with a 48V, 500w Bafang kit on the same bike (my daughter wanted an e-bike and I transferred the kit to a cruiser for her). There's good advice above about just building a mid, but other options may be viable too.