I thought your temps were ~55c rather than 67c. You definitely don't want to overclock at that temp, your already as high as you wanna go. It pretty much comes down to whether you want to spend cash at this point to upgrade your cooling.
If you don't want to spend much money, you could remove your heatsink and processor, clean them both with isopropyl alcohol (I use 70% because its what I have, higher % is recommended) and then lap them both using sandpaper and water (400/800/1500 grit).
Lapping Guide This guide walks you through it but he uses more grits of sandpaper than really necessary and he says not to use water. In my opinion, use a few drops of water on the sandpaper when your sanding, it'll slide nicely and despite his opinion you aren't going to ruin your processor, otherwise I would of ruined a lot of processors by now. Once your done lapping hsf and processor, clean them both again with alcohol and remount the hsf. You'll need to use some thermal paste, if you dont have any you will need to buy some unfortunately, but its only 7 or 8 dollars for a tube - I recommend OCZ Freeze or else try Arctic Silver five or else Arctic Cooling Mx-2. I bet if you do this you could lower your temps enough to do a light overclock, and it would cost less than 10 dollars and a few hours of time.
If you are willing to spend cash, I'd recommend ordering a new hsf - if you want a nice bolt through setup go for the thermalright 120 true (~60 Cdn) or if you want similar performance but the ridiculously awful pushpin mechanism, go with the Ocz Vendetta 2 (~40 Cdn). Either of those will lower your temps enough for some serious overclocking and overvolting. You'd probably wanna do the lapping with these as well to take it as far as you can, depending on your time and motivational commitment to the whole thing.
Another thing, you could try downloading speedfan and using that to increase the speed of your processor fan. I haven't used it (I use a bios tool) but it should work. Don't bother looking for a similar bios tool, there doesnt appear to be one for your motherboard.
Oh and one more thing, if you go the cheap route, another option is to get a large house fan and put it right on the open case and crank it up. It wont look great and its a bit fragile of a setup but I dont think any computer enthusiast can say they haven't done it at some point. Good luck with the overclocking and let us know your progress.