I would just buy a new deck and see what you think of the stock speakers with some power. I bought a $70 pioneer from Crutchfield and it really woke up the system. I then added an 8 inch sub with a small boss amp under the seat. It rocks pretty good.
I tried using high pass install first but had no remote wire. If you are into rigging stuff up you can run a jumper wire from the positive on the amp to the remote and put a toggle switch in between them. That would be a pain in the butt though.