Just drive right on past the S. Fork of the Holston (in VA) and head to the South Holston River near Bristol, TN. That would be my destination if I had a 6 hour radius driving distance from DC trip to plan. I hear very good things about the Delaware though, Art can attest, and I imagine your wheels are already in motion, but if weather forces you to adjust.... Back to the South Holston for a moment, when there's no generation happening, you can wade clear across the stream (like 100+ ft in most places) and fish to rising fish all day. They munch sulfurs this time of year, but there are also midges and blue wing olives in other seasons. Fishing the South Holston, its very spring creek like in that the currents are a gentle meander (again, assuming no generation occurring), and the water is exceptionally clear, but the key difference is the bottom is firm and wadeable, albeit slippery from the didymo. You have a lot of options in the area; you could mix it up by heading to the Watauga River or checking out blue lines in the area, and I'm sure there's bass fishing around as well.
Regarding the South Fork of the Holston, it's a much smaller stream with less open water. I checked it out one time, and did ok. It's primarily stocked rainbow water (Buller fish hatchery is situated on the stream), the fish naturalize really well, and get to be mega sized. But you gotta fish peanuts to them (by which I mean, midge larvae imitations). The fish I hooked into were like 16" but only after I fished through all the water once with typical setups and got zero looks. They're just on the midges alllll day. There are thirty inchers in there. But there's not a ton of water, and if you're going that far, keep on going to the South Holston, which is epic and worth the multiple day exploration trip.
I need to try the Delaware. Throw it on the pile.