I want to progressively upgrade my system in my 2000 Jeep grand cherokee Ltd. It has the factory installed Infinity gold system now, nothing that great at all. The two dash tweeters were recently replaced with new JL audio ones. I think my next step might be to replace the rear door speakers, though i am unsure with what. To me, the system sounds too muffled, though the highs are better with the new JL's. Any suggestions on a course of action.. Thanks