Ok I am on the beg for some help! I have a 98 Jeep Grand Cherokee Laredo which I will be shortly be giving to my son as his first car. It had a factory head unit with four factory speakers. One of the rear speakers is dead (checked by switching it for a front and it does not work there either!). So I decided to "ICE" it up a bit for him! I put a new head unit in it which works fine, and a colleague at work gave me a new 550 watt 2-channel amp with 4 new three way 6 34" speakers which will fit the Jeep. He was clearing out after his son left for college and told me to get them fitted quick before his boy comes home for them - nice! I also have a slightly used Pioneer 12" sub in a box. The sub is rated 800 watts peak power (150 watts nominal). The four speakers are rated 135 watts peak each (50 watts RMS). I know I can run the sub on it's own in bridged mode on this amp. I also know I can parallel off the pairs of speakers (left and right) and use this amp for them, albeit that I would lose fade control front to back. I have also seen a wiring diagram somewhere for using the two channels for the speakers and also bridging for the sub but this seems dodgy. I think therefore that I need another amp. My questions are as follows:- If I can use a 2-channel for the door speakers should I use the one I have or would I be better using that for the sub and getting another one for the speakers bearing in mind the ratings of everything? Is the 550 watts enough to drive the 4 door speakers? Would it need to be a four channel for the door speakers to give me the fade control back? Will the fade even work if I am using the low level RCA output from the head unit to the amp? If I use this one for the door speakers, do I just need another bridgable two channel amp for the sub woofer rated at up to 800 watts peak output? Anyone know where I can find a formula for all this stuff (and the money to finish it now I started it? Thanks in advance - if you can't answer all of them at least answer some of them!!!! Cheers.