The ap1 s2k's are notorious for awful sound systems, but what are the best speakers to replace the stock ones? thanks

 

Best is subjective. Please quantify the word "best".
Head over to Crutchfield and look around.

 

Depends if your going to use the factory head unit or aftermarket. Or if you addy a aftermarket amp.

 

Go to a car audio store, bring your favorite CD, check out the speakers on the demo board, buy the ones that sound the "best" to you.

Replace the stock HU with an aftermarket "high power" HU, in fact, just replacing the "low power" stock HU with a "high power" aftermarket HU will make a huge diff. even with the stock speakers, just replacing the speakers, [and using stock HU] can end up sounding even worse. 94