Stock HU and aftermarket speakers

The last car I had I matched up the impedence with the speakers and head unit, all in all a straight foward and easy process. I've recently bought a new car and I like the stock head unit, plus it also houses some of the other features of the car such as the stock secruity system.

I was wondering if you can hook up aftermarket speakers to the stock unit.  My car is a 2000 malibu and I'm looking at putting in infinity kappa's. The 462.5cfp's (4" x6" ) up front and the 692.5i's ( 6" x 9" )in the back. Both speakers come with built in crossovers. The impendece of these speakers are 4 ohms. Can I hook these speakers up to the stock unit?

Of course, if any one has ideas or suggestions about how to replace the stock head unit and maintiain features such as the alarm system, I'm all ears. 

I wouldnt reccomend hooking up kappas to a factory stystem. Trust me you will be wanting more power for these great speakers. Try using an LOC on the front and back speaker outputs on the factory deck then using that signal from the factory radio run it to a good 4 channel amp (JL e or / series or Rockford Fosgate). This will give you the power those speakers like. And why are you wanting to keep your factory radio for. They suk ,so I would reccomend doing the first option as something temporary if you do ,and then upgrading to a good Eclipse or Alpine Head-unit. Aftermarket head-units play CD much better then your stock deck and they have more features and options also.

ohh yeah. since your car is a 2000 then it might have a class 2 data bus system in it(this means that your radio is sending the door chime and other warning/alert sounds through your front speakers right now. A simple way to find out if your car does have this system in it is to listen to the front door speakers with the door open. If you hear a chime coming from the front door speakers then you have a Class 2 data bus system. People like PAC make interfaces that let you still hear the chime and warnings. Another option is to relocate your factory deck but I dont really like this idea because you have to run a big wiring harness to where ever the radio is relocated to. Only do this if you dont want to buy the PAC interfaces.

customsuburb - do you have any links for the PAC interface?

I like the idea of compeletly replacing the head unit, just want to make sure I don't loose any anything in the process.

I looked around a little and it looks like your malibu actually dosnt have the class 2 data bus system. You wont have to buy any special stuff since it dosnt. If you want to make sure it dosnt just try the test i mentioned above. You shouldnt hear the familiar door chime through the speakers if you dont have the class 2 data bus system. Go to the link below to look at the wiring harness and any other stuff you will need to install your new cd player. It looks like the kit you will need to install a new radio sticks out of the dash a little because the factory radio opening isnt deep enough. Otherwise nothing else really different from any other radio install. Hope it goes well!

Stuff you need for install of cd player:

http://www.crutchfield.com/cgi-bin/S-cxLD2ytYAxp/ProdView.asp?s=0&c=11&g=112200&I=120923300P&o=m&a=1&cc=01&avf=Y

http://www.crutchfield.com/cgi-bin/S-cxLD2ytYAxp/ProdView.asp?s=0&c=11&g=103000&I=120701858&o=m&a=1&cc=01&avf=Y

http://www.crutchfield.com/S-cxLD2ytYAxp/cgi-bin/prodview.asp?i=12040GM10&s=0&cc=01