I bought an aftermarket sub and it never sounds right to me. Had to use an LOC since no RCA outs, and it's always boomy to me and too loud at lower volumes and too quiet at higher volumes.
I have the additional speakers and amp for the rest of the car sitting in my house.. but I think I won't be happy until I get a new H/U. I miss the old $150 single DIN units.. now the NAV units I want are in the $1000 range
If I had to do it again I'd probably start with sound deadening.. then maybe the oem+ and just be done.