power booster won't make it stop better. your foot will just be a liitle less tired when you hit something.
you need to figure out why it doesn't stop so good. to hard or soft of pad from wilwood? what exactly is "stops like garbage"? from 50 mph how far does it take and how many hard stops can you do before they fade? just when they're cold or just hot? are you locking the rears way early or not at all?