I went and bought the HU I wanted and then bought a nice 4 channel amp. I also removed all the rear speakers and installed a nice set of 6x9's. It was a personal choice because I plan to get rid of all the bose equipment in my car. I then wired in the HU like you normally would. Then wired in the amp to the HU like you normally would. Then in the trunk where the bose amp is I found the wires that go from the bose amp to the speakers and wired those wires to my new amp using the 4 channels of the amp to control the 4 corners of the car. I still have the wireing diagram that tells you which wires are what in the connectors at the bose amp. Also there is a remote wire that goes the the bose amp. I used that wire for the remote on my new amp, I just had to wire it in behind the HU. If that doesn't make sense let me know and I will try to explain it a little better.
But if you plan on leaving the bose speakers in the care I would splice in some RCA's and wire it up that way. I did try it this way but since I was getting rid of the bose amp the way I did it made more sense.
If you do it with the spliced RCA's it is much easier. I just spliced in some RCA ends on to the speaker wires behind the HU and plugged them into the RCA ports on the back of the HU. Either way let me know if you need more help, it has been awhile since I did mine but I will help you the best I can. Hope you found something useful in that mess I just typed
