My Bose has nice all around sound . Good enough bass and way better than most stock radios. Of course there are way better options for aftermarket and lots of $$$. I like by Bose and think it sounds great.

 

Last thing I would upgrade in this car. My wife believes I'm deaf n I need to continue the rues...

 

It's very very difficult if you want to DIY. I would take it to an experienced installer to do the work (i.e. not a chain store.) To answer your question:

The Bose system has a special Bose amplifier that adds a) functions as an active crossover, and b) adds equalization to correct the interior cabin response + the loudspeaker driver response. There's also the Bose powered subwoofer, which I'm not sure you get with the non-Bose. The active EQ actually is a very important part of what makes the Bose system sound passable, especially given the cheapo paper-cone drivers they use and the non-ideal mounting locations.

So what you would need to exceed OEM Bose sound quality is really an upgrade of the front loudspeakers and the addition of a subwoofer. In order to practically accomplish this, you're going to need to add an amplifier as well. With the non-Bose OEM head unit, I THINK there's a way to tap a low-level analog output signal to feed your aftermarket amp. For a 997.2 with Bose, you can't, and there's no aftermarket solution - which means you either have to replace the headunit or tap the equalized speaker outputs from the Bose amp itself, send it to a processor for summation and de-Eq, and then to your aftermarket amp. Regardless, I would also highly recommend a processor that has "room correction" (similar to Audissey in home theater), like the JBL MS-8 or Alpine Imprint solutions, since frequency response problems are very important in car audio.

All of that being said, I think others here are right - you probably limit the buyer pool of your car come resale, because some people will want the Bose system. The reality is, most consumers have the same mentality of the customer in that hilarious Youtube video posted by Oli928, for what it's worth. OTOH, many potential buyers could also care less about the stereo (the evidence being that in all of these stereo threads, someone will ALWAYS say something like "the best sound is rolling down the windows and listening to the exhaust.")

Let us know what you decide!