well, you can basically run as large of an amp as you want, and you will get your window flex, just have to make sure you have good connection to it, to keep it from frying, however, it is all up to your own behavior not to push it beyond what your system voltage is supplying. don't lie to yourself either. are you honestly going to keep yourself from turning it past a safe level? if you can't then paying extra for a real nice amp, is just going to cost you that much more when you do blow it. if you think you may just blow it, buy one that you are more comfortable blowing. that's what i am getting at.