I've just picked up a Radeon HD6950 that I flashed to the 6970 bios. That seems to be working great but I've noticed that I'm only hitting 60-70% of the GPU pretty consistently (regardless of which bios I use).
I'm currently running an Intel Core 2 Duo E6700 and I knew I'd likely be CPU limited but the 6970 was the two generation upgrade from my old 4870 and I wanted to get in on the unlocked 6950 mistake before they fixed it.
I just checked my Motherboard, a Gigabyte P35C-DS3R and it will support a Q9650 (about $300) which is a pretty beefy processor upgrade according to the CPU charts. It's in the top rung which is 4 above my current proc. I wasn't planning on upgrading immediately as I expect that I would end up with a low end i7 a new mobo and new tri channel memory but with this option it might be significantly cheaper and is something I can do now if I want to.
The problem I have is that the Q9650 is a pretty old processor so I'm not sure I should drop the $300 now instead of waiting another 6 months to replace the guts of the system in whole.
As the motherboard is the C revision, I'm already using 4 gigs of DDR3 memory but it's only dual channel and as it's some of the first DDR3 memory I suspect the timing on it sucks and will be hard to find a compatible stick to use with a tri-channel board (if that's even possible, I haven't looked up the tech differences yet). So I suspect if I upgrade later to an i7 I'll be out the Proc (about $350) a new mobo (about $200) and 6 gigs of ram (about $200) or $750 total.
I was hoping for some advice as I'm pretty happy with the machine overall but I wouldn't mind seeing it run just that much faster.
The Q9650 is a beefy processor, but it's not worth the $300 premium IMO (and this is coming from a Q9650 owner).
If you really want to extend the life of your 775 system for a few years, I would look for a good deal on a used Q9450 or Q9550 on eBay and overclock it. By good deal, I mean don't spend over $150-170.
I upgraded to a Q9650 from a first gen E6300 and the boost was phenomenal. That being said, I use software that uses more than 2 cores so it was worth it for me. Yes, games were improved... but not by as much as a video card upgrade would bring.
I forgot to ask... are you running stock on that E6700?? If so, OC is your short term solution.
I vaguely remember trying to OC the comp when I first built it four'ish years ago and that it didn't respond well to that. I was planning on going home and trying that again tonight as the current best solution. However, if I can pick up a Q9xxx series for a under $150 I'll consider going that way.