I think since you are in an active bike market your budget could buy quite a lot. There are eleven hundred bikes on DC Craigslist. One of them is fine. Take a moment to notice you are heading down the path not of "saving money riding a bike" but rather "identifying as a Bike Commuter" which is how we get targeted to spend more.

But it's nice to have something new(ish). I know from experience it's hard to keep up, much less upgrade a Hardrock, without going whole hog. The individual pieces are all the kind of hokey that goes together. When you want to replace one worn out part with a current part, it tends to cascade to the rest of it, until it seems foolish next to the price of a new bike. And current bikes have some good features.