Slowly, but surely, going through my 720. Decided to do the stereo next.
The previous owner had done a poor job while installing a Kenwood receiver. Hacked the receiver housing all up. I would have considered leaving it alone had an electrical short not given me problems.
He left the stock front speakers, but ran rear speaker wires back without speakers, so speakers were very easy to install.
Installed a Pioneer DEH-S5120BT receiver. Polk 4" DB402 front speakers, put some foam in the panels to deaden, then used RTV sealant around the speakers themselves. Doesn't really matter what they look like because I'm putting the kick panels back on. I also used 4" speakers again because of the kick panels. Threw some Pioneer boxes in the rear.
I'm very happy with the overall sound. Nothing extraordinary, but certainly beats what I had!