Actually running the power wire near speakers shouldn't matter all that much. Just make sure to keep it away from the preamp wires and use a good quality shielded preamp cable. Using cheap ones is just asking for noise. Also try to keep the ground cable for the amplifier as short as possible. 12-18" is about the maximum length you want to use. A good way to test for a good ground is to use a multimeter. Put the red and black probe on your battery with the car off and measure the dc voltage at the battery making sure that the power wire is tightly attached to the batter terminal. Then go to the back of the car and do the same with your power wire checking various grounding points. The grounding point with the greatest potential difference is probably your safest bet for combating noise. It is usually locate near or on a seatbelt bolt since those are connected to the thickest portion of the subframe. One more not that was stated already. Amplifiers are not meant to be mounted upside down. I have seen it done before, but hot air rises and it is being forced right back on to the heatsink. Good luck with your install, i hope i have been of some assistance.
Cheers
rimmie
