Ive left mine as standard, mine are excellent!!! really bassy and crisp clear. i run them on a pioneer DEH-8600MP.. i just run them on the high pass filter, so no distortion, and JL AUDIO W3 sub on a LANZAR Amp. runs sweet!
 
Unless you're fixing broken ones, or you're running an amp, I seriously woudln't bother replacing them with aftermarket ones. The OEM ones are very good.