Would airfare be separate? $2000 would get you $95(79 Euro)/day for 21 days or $71(59 Euro) for 28 days. If airfare is separate, I'd definitely say that you have enough. Average about 20 Euro for a hostel, 20 Euro for food (can be done a lot
cheaper), 10 Euro for drink (assuming you drink) and you're at aroudn 50 Euro, not including transportation around.
You'd might want to look into a railpass when you nail down what countries you'd like to visit or just get a 21 day unlimited pass for $495 (assuming you're under 26 [there's also the flexi pass that would give you 10-15 non consecutive travel days for 451/594 respectively]). You might not think a pass is cost effective and can just travel point to point (I found it to be about 80 Euro for an 8-12 hour trip [Frankfurt-Lyon, Lyon-Barcelona, etc]; obviously it varies to some degree). You can't really get an accurate price for train trips online.
on the otherhand has their prices listed on each website. The prices are good and I had no problems with the bus.
Okay, I've just gone into way more information than you asked for.