Help deciding on a deck
 

I am buying a deck for a new car I bought and I need some advice. I am looking at the Alpine CDE-9874 and CDA-9884 but can't decide. The 9874 has 16W RMS and the 9884 has 18W RMS, am I going to notice a difference? If I go with the cheaper one (9874) will I have a problem later if I want to add a subwoofer for example.

Any thoughts would be appreciated.

Thanks