I recently bought a 1987 mustang gt. Im looking to replace the speakers in the stock enclosers. I will probably get subs at some point but I dont have the budget for it right now. Can anyone suggest what to look for, for the best sound or explain RMS watts vs normal watts, frequency responce and all that stuff so I know what to look for. I belive the speakers are 3 1/2" in the dash 5 1/4" in the door and 4"x6" which can supposedly fit 6"x9"s in the back. I recently had a JVC cd player put in. Is there anything else i would need?