Audio Speakers: Replacing Speakers In 05 Malibu?

I’m planning on replacing the factory speakers in my 05 malibu but I have no clue on whats needed for the system I want. I’m planning on outfitting the entire car with Clarion equipment. I know what speakers and subs I want but I’m not sure what to look for when it comes to setting up an amp. I’m keeping my factory stereo cause its linked to my security system, auto start and other stuff that’s needed for my car to work and I can’t find a stereo that would handle all those features.
So to make a long story short I need some assistance finding out what type of amp I would need to hook up to a 600 watt Clarion sub, 220 watt 6×9′s and 180 watt 6.5 round speakers.
Also is it a good idea to keep the exisiting wiring that’s already in my car or should I replace all that as well.
Any advice on this would be great
thanks