Short answer: the only thing a stock DR650 needs to be a good street bike is a better seat.
Long answer: I bought my DR to replace a vintage Yamaha DT250 as my dual sport bike. On the ride home from the dealer, I was so impressed with the DR's street performance that I ordered a Corbin for it. Once the seat arrived, I took the tailbag off my WeeStrom, put it on the DR, and took off for a Blue Ridge Parkway tour. It handled that ride so well that I sold my Wee when I got back. Now my DR is both my dual sport bike and my street bike of preference. I have also added heated grips which let me ride the bike in the winter comfortably. I've also made a number of modifications for off-road performance, but none of these are needed to make the DR a good street bike.
I don't like windshields so that is not an issue. I find the OEM Trailwings to be an excellent 50/50 tire, I can go asphalt dancing all day in the twisties, and still ride all the dirt I want (just no mud). The Wee had a better engine but nothing else about the Wee was as good for me as the DR. I have really enjoyed this bike and it is as close to a do-it-all motorcycle as I have ever owned in my 38 years of riding.
"Reason takes a holiday as Dr. Horrible spends money he doesn't have, on a motorcycle he doesn't need, in a misguided attempt to recapture his youth which, upon reflection, wasn't all that great in the first place."
"Ride to the bar in your pirate outfit, guzzle some beer, play "Free Bird' on the juke box and then go home. Badass."