I'm about to buy a 2002 s2k and I'm just wondering how the stock audio system is. Also, what brand(s) would you guys recommend for speakers and a head unit?

 

stock sucks

 

Speakers are subjective, you really need to listen for yourself. Having said that, I like the Alpine Type-S, Type-R and Type-X's (have to run an amp for the X's and the R's IMO, S can work off a replacement HU), Infinity Kappa's (2ohm, amp again), Focals (amp), and some others. I don't like the Polks but many people do. It completely depends on what you listen to and what kind of sound you like, so audition the speakers.

For the HU, do you have an iPod that you want to use in the car? If so, Alpine CDA 9856 or 9857, the fullspeed control is the best interface out there for an aftermarket HU.

if not, you have plenty of choices, I like Naks', Alpines, Clarion Pro Audio and a few kenwoods. Depending on what you want will determine what price range you are looking at.