this is not for my own car, but if i wanted to wire an amp from a factory head unit with XM radio, what would you guys recommend that i do for the following:

remote wire?

rca jacks? (can i just tap them off the rear speaker wires?)

TIA

Does the car have a power antenna? If so, check to see if it stays up when the CD player is on. If it stays up all the time, you can tap the remote wire off of that. If not, you would have to tap it off off the acc wire (ignition). The only problem with that is that the amp would stay on when the car is on, even if the radio is off. You can wire and external toggle switch to fix that. As far as the RCA's are concerned. You can tap off of the rear speaker wires, but the amp would need to have speaker inputs. If not you would need a low level adaptor. Hope this answered all of your questions.

yea, when i put in my amp with my factory head unit i just took some power off the rear speakers...but then again mine had RCA and speaker inputs. i did the toggle switch mod for mine. i coulda used the remote wire but i dont always wanna listen to my subs so i can just turn them on or off as i see fit. i tried my RCA jacks after i got my new head unit and they dont put nearly enough power so i went back to taking the power off the rear speakers...that what i did anyways.

You will get a cleaner signal off of RCA's and did you check the gain on the amp? The gain knob actually effects the amount of input to the amp. That might of been your problem.