There is nothing wrong with an '08 Adventure if you find and pick the right one. My '08 that I bought a year ago from Oregon had Akro's, crash bars, Happy Trails rack, heated grips, rear KTM topcase and 10K miles. It was less than your quote. I also got the stock seat and windscreens as well as the gel and touring windscreen. The PO was meticulous with maintenance and it was a far better bike than the newer/more expensive models.
Edit: I forgot about the Cycra ProBends and I'm sure there's some other upgraded bits escaping my memory. My point is that there are very well sorted used bikes available for far less than it will take to sort them yourself.
YMMV but you can do very well if you know what you want. BTW, I still have the '02 GS, it's also well farkled and runs like a scalded cat. But I would never abuse it in the dirt the way I will run the Adventure.