You don't need to take the Acela from DC to Baltimore. It's only like 45 minutes on the regular Regional train from Union Station in DC to Penn Station in Baltimore. Acela only really even cuts 30 mins off the trip between DC and Philly. Acela is about 80 bucks round trip and Regional is 30. But if you want to save a whopping 10 minutes each way for 50 bucks, hey go ahead. Also the Acela trains don't run as frequently.

Where in DC are you staying and where in Balitmore is this DJ going to be at? There's all kinds of loungey type shit in DC (it's not much of a club-oriented town...all lounges) so there'll probably be other solid options even if you don't make it up to Baltimore to see that particular guy...