Thanks for the advice. now I have a few more questions because now i'm really lost. as I mentioned before I have two srx 715s and the srx 728 with two xti 4002 and one ITech 6000. you mentioned not to use the drive rack pro pa+ for this setup. with this in mind how do I setup the system to run the 715 in bridge mode one with each 4002 and how do I setup the ITech 6000 to run the 728? what settings do I need to make in the amps to have them run this setup clean and efficient. thanks