If you're losing the amp and want to have your polks (and maybe your sub, if you don't want to sell it, and depending on its size) sound good, I would go with colin's recommendation of the Panasonic. It may not be Alpine or Pioneer, which is what is typically recommended here, but it has the built-in power of an external amp. I think you'll be able to tell if you move from an amp to just an aftermarket HU with only 22Wx4 or so.
