I have a Q6600, and 6 mounts ago, I also had a geforce 8600 GT, which it's almost the same sh*t, i could barely could play on HD on dx9...
I bought a geforce GTS 250 (second hand, and also very cheap) and now I can play in Full HD on dx9.
Q6600 will buy you some time, it's a great CPU, but unfortunately it doesn't have SSE 4.1 and due to the lack of memory controler on die, many applications works much better on a i3 with only 2 cores, and MAINLY GAMES. This days it a total waste of money (and i'm writing you while i'm using one of those).
The graphic card is by far your best option. Don't waste more money on a socket 750, is already dead, an i5 it's almost twice as fast as a Q6600.
My advice would be: after getting a new graphic card, get a phenom II 950 or newer (FX, etc), or if you can afford, get an intel i5 3XXX (ivy bridge)..