I am contemplating on upgrading to a quad core cpu. Besides gaming I use my computer for 3D modeling (pro/e and some autocad) and ANSYS (FEA) and can get an advantage from multiple cpu's. What I am trying to decide upon is whether to get the Q9300 or the Q6700. I want to OC to 3.0 to 3.2 GHz and am pretty sure both will get there. I have an x48 Asus board with crucial DDR2 ram so I am not really FSB limited. Since both are the same price and stock speed, does anyone know if the extra L2 cache is worth the added power consumption of the 65nm device?

Get a 6600 and save yourself the coin. It will easily hit 3.0-3.2. 9300 just isnt worth the money.

I looked at that one first because of the price but it seemed that 3.2 was about as fast as most people got them to go and had to use voltages at or above 1.4V. At this level the processor might produce more heat than I would like as I enjoy having a very silent system. Although the 65nm die has been in production for awhile now and maybe that voltage has come down with the G0 stepping. Does anyone have experience overclocking a Q6600 to 3.2 GHz with a G0 device and if so what voltages are you using?

Agree. Zero point to the Q6700.
Only get the Q9300 is power/heat dissipation is important to you.

It looks as though the Q9300 will hit 3.2GHz at about 1.25V to 1.3V and a Q6700 will require 1.4V. I know my E8400 running at 3.95GHz 1.38V never really gets above 52c or 53c when fully loaded so I suspect the Q9300 would do the same down at 3.2GHz. I've herd of overclocked Q6700's getting up to 65c and beyond. Will probably go with the Q9300 as the extra L2 cache is probably not needed.

The Q9300 is a newer version w/ less speed (2.66 vs 2.5) but the 9300 has 1333 FSB not 1066 FSB, and has the 6 MB L2 cache, and it is 45 nm so it's better

The Q6600 has NO problem going above 3.2 with slightly tweaked voltages. I've had mine hit 3.8 but backed down because of the temps. Q6600 is the best bang for the buck at the moment, and unless you really feel you need a 45nm proc right now, go with the Q6600 not the Q6700. There are numerous guide on how to overclock the Q6600 stably, mine only needed to go to 1.325V.

At the same price and same OC the Q9300 is 5-7% faster. So to answer your question. The Q9300 is the better choice. That said, if you want max OC the Q6700 is the way to go due to the FSB limits on the Q9300. In two of my Shuttle boxes the Q6600 clocks at stock vcore 9x333=3ghz. You might also look at the XEON Quad core's.

Q6600 3.2GHz 1.4V. I'm pretty happy with it. Didn't try to seriously overclock it. Can run a bunch of stuff with my 8GB of ram and not slow down. All that for $220.

I'm running my Q9300 @ 3.0 - 1.32v and 42°C. OCing was as easy as setting the FSB to 1600Mhz from 1333Mhz. I did have to update my BIOS to make it run stable, but no problems after that. I had OCed to 3.4 but I saw no need in that big of a jump so I came back down to 3.0

Most G0 Q6600 seem to hit 3.5-3.6 GHz on air. One person here has hit 4GHz on his.

My Q6600 runs daily at 3.0GHz at stock voltage with the retail Intel fan, and in a Quiet and fairly small Antec Sonata II case. I have not hit a wall overclocking it but decided to hold off going higher to keep the load temps under 60 degrees. When I pull the mobo and install a differnt fan, I'll push it higher.

edit: Yesterday Fry's had the retail Q6600 for $200. It was $186 shipped a few weeks back. That's really quite the bargain IMO. Today their price is back to $259, so check Zipzoomfly who seems to be a few bucks cheaper than newegg lately on them.