I had Q6600 before I moved to E3-1231V3.
1. Head to eBay and look for second handed RAM and make your RAM to at least 8GB. 16GB would be nice too.
2. Try to OC your Q6600 and see how high your Q6600 can go. Mine was 3.3GHz stable for daily+gaming usage, I got a room heater as bonus tho'...so...extra useful for winter.
3. If you see problems due to VRAM, you can simply drop the resolution and some other settings.
Using those 3 points, you should be able to make your Q6600 better and should solve some gaming issue, if your Q6600 falls slightly below minimum requirements.
If your PC falls below minimum requirements, it does not automatically means that your PC can not run the game. It is just not guaranteed that the game will run. Meaning: You can simply try and see
Full upgrade plan is still recommended tho'.