I was in your exact position a few months ago. My Core 2 Duo E4300 wasn't cutting it for new games like Crysis 2 or LA Noire even though I had it overclocked +66% to 3000Mhz, fairly close to the same performance as your E6750. So I decided it was time for an upgrade, and I set out looking for the cheapest CPU that could handle any modern game at around 40 fps or more.
I was all set to buy a brand new cpu+motherboard+ram kit from newegg, but at the last minute I checked on eBay and I found it was cheaper to just get a quad-core cpu for my old socket 775 system. After all, I already had plenty of fast DDR2-800 memory and I was 100% satisfied with my Gigabyte 965P-DS3 motherboard, so why chuck them out if I can still make use of them? Instead of paying $230+ for a Sandy Bridge Core i3 2100 kit, I just bought an old Core 2 Quad Q6700 for about $125, and sold my old E4300 a week later for $25 to recoup some of the money I spent. The Q6700 is great... it's basically two E6750s glued together on one package, and at stock clocks it is about 90%-100% as fast in modern multi-threaded games as a core i3 2100, which would have cost just as much as my Q6700 for the cpu alone
, never mind the new board and memory I would need. And really I probably paid a little too much for the Q6700 at $125... if you are patient I bet you can get a used Q6700 for $80-$100 off eBay or maybe Craigslist. One tip if you go the used route: make sure the cpu was just pulled out of some some boring office workstation computer from 2007. You do NOT want a cpu that once lived in some 14-year-old's gaming pc that was overclocked to the max with some $20 off-brand power supply.
The TDP for the Q6700 is 95W because it uses the dual-die 65nm "Kentsfield" design, but even so I think your Scythe heatsink (good choice on that, by the way...) should have no trouble handling 95W quietly. But if 95W still sounds like it's just too much heat for you, you might want to look into the 45nm "Yorkfield" chips, if I recall correctly they vary between 65W and 95W. Be aware, though, that not all socket 775 motherboards will support 45nm CPUs, even if you flash to the latest BIOS
. You'll want to check with your motherboard vendor to make sure that your model supports 45nm chips (my Gigabyte 965P-DS3 does not support them, else I would have purchased a 45nm Q9650 with a better clock rate and more L2 cache than a Q6700).
Oh, just remembered something about the Q6700 - if you leave it at or below stock frequency (2666 Mhz), it will almost certainly tolerate a good deal of under-volting, (your motherboard almost certainly supports voltage control if you can overclock with it). In my case, stock voltage is 1.27500V, but I got it down to 1.12500V, totally stable through 72 hours of torture testing. This reduced the cpu power consumption from 95 W to 73 W, based on this wattage calculator
Lately I've been gaming with headphones, so noise is not much of issue anymore, and I've found that I can get my Q6700 up to 3333 Mhz at 1.40000V (this is on a mediocre Thermaltake i1 heatsink) completely stable through 72 hours torture testing, temperatures between 44 C idle and 77 C full load, (last I checked, the "Kentsfield" Core 2 Quads are good to go at any overclock so long as they stay both under 1.50000V and under 80 C). At this overclocked speed, my 5-year-old Q6700 beats out a Core i3 2100 pretty handily. Overclocked, my Q6700 consumes a ton of power at 143 W (+51% more than stock power consumption), but it's getting chilly at my latitude this time of year and I could use a space heater anyway
:P. Still, the +25% boost to clock speed is very noticeable when paired with my Radeon 7850 2GB, especially in cpu-heavy games like LA Noire and Deus Ex: Human Revolution. Btw, the Radeon 7850 is an unbeatable mid/mid-high range graphics card if heat/power consumption is a concern... it's noticeably faster than a GTX 560 Ti and it trades blows with a GTX 570, but it accomplishes this with a TDP of only 130W (!)
... and it has double the VRAM. The MSI Twin Frozr 7850 has a particularly quiet heatsink/fan and it's also very overclocking-friendly.
One aspect of the the low to midrange Sandy Bridge / Ivy Bridge chips that shouldn't be overlooked is that the clock generator has moved from the northbridge to the cpu, meaning that YOU CAN'T OVERCLOCK THEM
, not more than about +2%, not even on a deluxe $300 motherboard, at least not unless you buy a $250+ "-K" model with an unlocked multiplier (and of course, those "K" models are all top-of-the-line to begin with, faster at stock clocks than any gamer could need right now). I can't help but hate the idea of having unused performance potential in my computer... I hate it almost as much as I enjoy gaming... Looking at forum threads where people post their overclocks, I'm finding that back in 2007/2008, when Core 2 Quads just started hitting stores shelves at $800-$1000, overclockers could achieve 3600 Mhz or 3800 Mhz at around 1.40V to 1.5V on a decent air cooler like your Scythe (4000 Mhz was pretty achievable on water, too).
So long story short, if you have a decent motherboard and enough ram running at a reasonable speed, it will probably amaze you how much of an improvement you'll get just by replacing a 5-year-old CPU with an equally old CPU. People are getting rid of their old Core 2 Quads in droves, and it's a buyer's market out there.