Knight Sacrifice to pry open the center?

Was it a sound sacrifice to break open the closed pawn center? It seems to me that I did the right thing. Also is there a way to counter the knight-in-the-center-supported-by-two-pawns-move? I absolutely hate it when my opponents do that b/c I simply don't know how to respond. Feel free to chip in ideas. I appreciate responses from everyone regardless of their rating. 

I should have done comment after the move not comment before the move. 

bump

I agree with NaturalDisaster.  The best move for white would have been to trade the e5 knight for the d7 bishop.  This would have simplified the position, allowed time to consolidate, and probably won the game with a 2 pawn for a knight advantage.

The sacrifice is completely unsound: you can't expect a real compensation when you just have your Queen attacking, and you'll never have the time to bring more pieces to the attack. White can refute the sacrifice in many ways.

I understand that White responded in dubious ways. Had I not realised that I would have commenced this sort of sacrifice more frequently. Thanks for giving me tips. 

I used to play the Stonewall attack myself but after playing it 1000s of times I found the games slow and boring. More problematic than that I do not know the effective counter to the stonewall attack. I guess I can castle queen side or play king's indian defence setup to thwart the white's attempt to unleash massive kingside attack but is there a way to actually pry open the center using brute force? If so can someone recommend me an opening or moves that break apart stonewall? 

White has no "massive kingside attack". The whole system is very committal, as a matter of fact the Stonewall defense is more ambitious- for a simple reason: Being a tempo up, white has made some concession with his pawns (like playing either g3 or e3 with the bishop on c1). If Black is able to put the bishop at g4 or f5, then he has more than equalized: e4 is a permanent hole, while e5 isn't.

Latest Stonewall attack I played as Black was a boring affair:

Hard to tell where white made the decisive mistake. Probably at move two.

Very bad sacrifice your "follow up" worked because your opponent misplayed a now winning position.

I always found knight on e5 supported by two pawns annoying. Taking the knight would give the White a pawn chain + semi open f file + pawn majority in the center. Not taking the knight however seems to me a bit dangerous, for the knight on e5 is on a good outpost. Although I know that my knight sacrifice (refer to the first post) was dubious, it was my way of experimenting a way to remove that knight. If prying open the center with force is difficult do I have to push either d pawn or f pawn to kick away that knight? 

Thnx for the response. Your point about 6...cxd4 has validity but I believe that his bishop's mobility is still restricted to be a viable threat even after he had taken on d4. To me, breaking apart the formidable pawn structure is of paramount importance in order to lead the game. 

I firmly believe that 9.a3 was played to support b4 thrust. I base this belief on two assumptions. (1). The white played stonewall structure, meaning that the player likes the zigzag pawn structure. (2). Players playing stonewall usually opt to expand on the queenside (at least that is what I think). 

To refute your point about a3 move: There is no reason to stop my knight from coming to nb4 when there is already a pawn placed at c3. If your claim about stopping the knight is true, that player played it way too early. That being said I believe that my a5 move was a good prophylactic move to minimise the threat on the queenside. 

And I agree with you on the moves 13 and 14. Many kind folks explained to me that it was a less-than-good sacrifice.