Don't ask why, but for some reason 4ohm speakers work. I installed 4 ohm Kappas all the way around after some coaxing from a friend with an EE. You know what they say, you can't spell geek without EE. I have had them cranked with no problem. They do however drain the battery very quick. Sound is also great. As pointed out they do no completly fill the old space. But you can only tell from the back, my windows are tinted anyways. But sound is 100% better.