Hey there Kww1, we all need some more info to make any real recommendation. 1) o7 stumpy- full sus or hardtail? this makes a major difference in the most important part-the battery and where you mount it. 2) you looking for a hub kit or mid drive kit? do you know the difference? 3) what are you using it for? mountain climbing, commuting, or cruising down the bike path. 4) budjet $.....$$$$ you're going to have to make compromises, sorry, you can't have it all!
I have a hub drive kit on an 08 Diamondback response comp. it was expensive- $2k, the battery's heavy, it hauls a** (28mph), its bullet proof (2500 miles so far), Its an absolute blast to ride.