Ok guys, After many days of messing about I have finally wired my rear bose speakers and done my own bass woofer mod. Here are the pics As advised I took out and bypassed the Audi Boot Amp & Sub. OK I am a noob with this so after some reading I figured out how to keep the speakers and use existing wireing to power the rear speakers. Main issues are most aftermarket HU have a 4ohm setting, the two rear bose speakers are 2 ohm. In order to keep the speakers, I accessed the rear wires that came out the amp and used them to wire the rear speakers in series, this is not the ideal set up but was easiest and cheapest. By doing this it raised the impedence to 4 ohm. In order to gain extra base I got some woofers and used some more of the wireing that was available to get these up and going. This is all due to the fact my HU-amp was getting hot trying to run the bose speakers individually. If people have any questions Ill try and help but like I say, this is not an ideal set up, but a budget way of upgrading your headunit and keeping the rear bose in.