The 6.5s in my non-bose/monsoon pontiac are biting the dust. Once i upgrade my subwoofer in the back, im going to purchase all around new speakers, except the tweeters.

Orion XTR693 6x9s
Orion XTR653 6.5s

I know the head unit does not have the proper power handling for these, but i will buy an amp later on. My question here is, how hard is it to integrate speaker wiring with the factory plugs?

Once i can replace the HU, i will do so. I have OnStar, so i need the Metra GMOS-5; my question here is, will this retain the steering wheel controls as well?

And my last question, Anybody have recommended head units that retain all features when used with the above adapter or any other working adapter? I'd like USB and RCA output for subwoofer