I would suggest trying to get a G0 stepping Q6600. You can get the specific stepping version from ebuyer.
Sell the one you have to make some money back.
I have the G0 and a relatively **** cooler (coolermaster... £16 on ebuyer)
I can clock mine to 3.5GHz, stable, but the temp creeps up to 75 ish, so I keep mine at 3.42Ghz at the mo, which keeps my hottest core at 71C, which I find is acceptable. (I bet it would CRANK with decent cooling)
A slightly cheaper option still is more case ventilation fans. I have 2 big 140mm fans one sucks at the front one blows out the back. This helps quite a lot actually.
I have no idea about your case and if it would fit, but if you are happy @3.0 and want only a few degrees safety margin this may be the way to go.
My settings for this OC are...
Vcore: 1.475 (but this only shows as 1.42 on cpu-z, i think its cause of my nvidia board v droop?)
RAM Volts: 1.97V (kingston hyperX 6400)
Timings: 4,4,4,12
FSB: 1520Mhz
RAM: Sync Mode @ 760 Mhz
MOBO; P5N-D ASUS 750i Sli
Don't get too down hearted. I just found out that my 8800GT is CRAP. Runs at 85C at stock, and gets artifacts when stress tested. I actually had to underclock it because I was getting artifacts when playing a movie. Sh!tty bawbag.
I don't want to send it back because I ditched the packaging, and I would have to do without a decent PC until the replacement arrived (I have an older laptop I am experimenting with OCing at the mo though)
Anywhoo, its a bit of a lucky dip these things. I have a golden CPU, but the GPU is stuck underperforming.