Does that CD Player have an AUX input? If it does you wont need an amplifier, except for one for the subwoofers.
If it doesn't, you might as well ditch the Head Unit. Now, excuse me for being partial to Rockford Fosgate, but I'd recommend you get their amplifiers. I would buy a decent four channel amplifier to push your speakers. Then get a mono amplifier to power the subwoofer.
It's not a complicated set up.
Here's a few links for amplifiers I'd try: