I am upgrading my factory car stereo to after market that is largely Polk Audio based.
First, the stereo to be removed is the factory Bose radio from a 2005 Chevy Trailblazer. It isn't completely awful - the worst factory stereo I'd heard was from my factory Bose Infinity Q45 - but the existing stereo leaves me wanting so much more so badly. Is spend a lot of time in my truck (and plan to keep it at least two more years), so why not put some money into it, especially when I unload the truck, the heart of the investment can be removed and taken with me.
In any case, here is what I went with:
Kenwood KDC-BT958HD (My preference has been Pioneer, but I thought I'd give Kenwood a shot)
4 x Polk Audio DB651
1 x Polk Audio DXi 112
Added a capacitor also. Very excited - I am a Polk diehard (home theatre is all LSi, as is my computer 2-channel rig), and I expect this setup to sound pretty good.