I'm currently still on a LGA 775 system with a Q6600 with a GTS 250 and I was quite happy with my system but I decided that it was time to get a gpu upgrade.
I'm planning on getting a 7950 but I'm not sure if my cpu is strong enough to 'not bottleneck' my gpu. I'm planning to get a system upgrade in about a year's time.
So basically what I'm asking is:
1. Will my cpu bottleneck a 7950?
2. If it will, by how much?
3. Will it be better to hold on for one more year and get a new graphics card TOGETHER with cpu, mobo, etc.
The Q6600 is currently overclocked to 3.4 and I guess I can go further if it's necessary.
Depending on the circumstances, the Q6600 is typically plenty adequate for gaming when it's at 3.0GHz or higher. That does depend on what titles you play, as some (notably Skyrim and BF3) are very CPU intensive, but not much will struggle with a 3.4GHz Q6600.
I upgraded a friend's rig with a similar setup: Q6600 @ 3.8GHz + Asus P5Q Pro + 8GB RAM + upgrading from a Radeon 5850 to 7950.
Based on my experience with that particular build, I can say that you're definitely going to lose a noticeable amount of 3D performance as a result of the Q6600. We were getting nearly the exact same performance out of the new 7950 as the 5850 that we were upgrading from. At first I thought something was wrong with the rig because I couldn't believe a C2Q running at 3.8GHz would choke off the GPU that much. I had a bunch of spare PC parts laying around so I swapped out the Q6600 and motherboard with a Core i5-760 (paired with an Asus Maximus III Formula motherboard). I kept the Core i5 at the factory clock speed and after just a couple minutes of testing it was obvious that the 7950 was showing us the kind of performance we were expecting to see. The difference was day and night between the two CPU's. A week later, my friend retired his Q6600 and replaced it with a Core i5-2500k.
You'll still have a fairly strong rig with the Q6600 + 7950, but there's definitely a lot more potential left in that GPU if you pair it up with a newer CPU like a 2nd or 3rd generation Core i5.