For sure the Jensen brand of stereos lacks something in the quality department. Mine works OK, but sometimes has annoying skips in the CD player. It's not on the top of my list but at some point I plan on replacing it. From the internet surfing I've done, Concertone seems to be a pretty good option.
http://www.concertone.com/
Kind of pricey, but not that much more than what a comparable Jensen sells for.
The only other option would be to piece together car stereo components. But they will be smaller so you'd have to customize the existing opening or mount it in a new location.