The Bose is certainly better than the stock radio, I compared them with a CD. I found the stock radio has no clear highs. The Bose is better with that, but still not a WOW system.
The ideal would be to upgrade the amp and speakers in the stock radio. Upgrading the Bose becomes more difficult as the system is balanced for speaker locations and what type of speaker (tweeter/woofer) is located where.
I got the Bose and it's fine, but the highs could be better and the bass can get boomy.
I spent a lot of time in my car this weekend and toyed around with the settings. Once I turned off the Centerpoint, the sound quality is MUCH better. I really enjoyed the system this weekend.
The reason I originally turned it on was I did not like the lack of stereo separation with that center speaker. The Centerpoint helped with that. However, it adds a bit of boomyness and lack of clarity. With it off, the sound is much clearer, instruments are more clearer heard. I still don't like the lack of separation, but after attending a Heart concert this weekend, there was no stereo separation there either. Guess I've gotten used to listening to music with earbuds, which give you a lot of stereo separation, I guess it's unnatural.
The other thing I've concluded is that the quality of the music on Sirius XM is not as good as a CD or USB stick with decent MP3s. That's disappointing, even Pandora has better quality. I really like the variety on Sirius, but this may doom that subscription.
So, the Bose ain't perfect, but it's pretty good. Also, maybe there is something to the "aging" of the speaker cones that means better sound as they "settle in".