6. Nxb5!
Threatens a check with a discovered attack on the en prise queen.
4. d4 is preferred over Bb5+ because of 4...c6 (instead of Bd7) and the Bishop loses time retreating.
4. ...c6 is the answer, not 6. ...c6.
6. ...c6 doesn't do anything constructive, whereas 4. ...c6 wins a tempo.
Even if 4. ...Bd7, I'd recommend 5. ...c6 or 5. ...Nc6 instead of trading into a blunder.
Edit: 6. ...Nc6 also prevents white from the discovered attack.
Any player of the Black pieces who understands the defense would reply 4...c6, and your "aggressive response" simply loses a tempo compared to the mainline.
The only rated players I could find who played this line more than once were Marvin Woelk (762) and Marie Kristin Raulf (745), playing in the same "Under 10" tournament.
I was playing Chess Titans (Level 3).I attacked figuring that after the exchange, black would be behind in development...I proceeded to win the game though I forgot to write down all my moves (D'oh). It would be of great help if you guys could tell me something I missed, or even if I was not the first to play this line.