I just replaced my 12 JK "base system" speakers with the Kicker 77KICK10 upgrade from Mopar. HUGE difference.. Way more bass and much clearer highs with nothing more than a speaker swap.. I wasn't expecting much but wow.. Looking at Dr. Evils link, they may even be the same speakers, just re-named. I bought an 8" powered Bazooka tube at the same time but I'm in no hurry to install it because The sound is so much better already.
EDIT: NOt the same speakers as Dr Evils. The ones I got are 75 watt RMS, have a silvery cone and are made to factory fit in my JK. Three screws and they drop right in.