I'm planning on putting in some subs w/ amp in. Can this be done with the stock headunit??? I have the Concert (basic one). My car is a 99.5 1.8T (non bose) if that makes any difference...

Hopefully someone sees this....

 

Yes you can put your subs in with the stock deck, all you need is to get a high to low level converter and splice into your rear speaker. Or just take a couple RCA cables, cut of one end of it and splice into your rear speaker. Its pretty easy but make sure you splice into the right wire