Airjam,
I completely agree with JJB8675309's statements on your current C2Q 9450 being a bottleneck, at almost any OCed speed for a new sli setup with modern cards.
I also agree with him that 570's (factory superclocked or not) are the best bang-for-buck out there right now, as I currently have x2 570SC's.
While I also agree that 560's very overclocked can reach raw FPS of 570's in some games, sometimes, they don't share the raw bandwidth or memory frame buffer of the 570's. Additionally, OCed 570's are very powerful.
I also agree with the statement of the sandybridge (anything) being a better bang-for-buck that the previous generation cpus, I must make a note of caution on this.
The current sandybridge lineup is awesome for being only the mid-level of the road offering of this generation. But if you plan on running sli, the older generation still is the best for raw gaming. Here's why.
The current sandybridge cpus only run in x8 mode when running sli, not x16. You WILL bottleneck and holdback your card's performance if you plan on using anything faster than a 550ti. The bottleneck only gets worse as the cards get faster. here is an article about 5870s being bottlenecked by 4%. Keep in mind that this is an older card and this result only gets bigger as cards get faster.
http://www.tomshardware.co.uk/p55-pci-express-scaling,review-31780-6.html
Additionally, while I can't find the article, there's one about the 480 being held back by 8%. (in x8 mode)
Here's a sidenote. You will find my system in my profile or sig, try both. Anyways, a friend of mine built the exact same system as mine, videocards and all. But he got the 2600 non-k and an asus sabertooth P67 with 8 gigs of dualchannel ram. (it runs the same timings and mhz as mine)
We both did a fresh install (with updates and drivers) of W7Pro 64-bit. With 3dmark11, he scored 9341 while I scored 11522. We ran both our CPU's at 4ghz. The kicker? The only difference in our systems was my triplechannel ram and dual x16 pci-e slots. After declocking, further OCing, and fiddling with his cpu and videocard speeds, his score only changed by a few digits. Hence the bottleneck of the pci-e slots.
Now i'm not saying that sandybridge sucks, no way! Sandybridge clock-for-clock is 20% faster and uses less power than the previous generation. Additionally, it has usb 3.0 connectors on the motherboards, and supports EFI bios's. For any single card solution, it rocks. But if you really wish to run sli. Don't waste your money on very high end videocards only to stick them in x8 pci-e slots.
You have 3 options in my opinion.
1. Wait for the high-end version of sandybridge later this year with more core/speed/ quad x16 slots.
2. Buy an i7-950 and run sli (whatever cards you want)
3. Buy a sandybridge and run one single powerful card. Like a 580/6970/6990/590 and get the factory OC model if your not comfortable OCing.
I suppose the last option is to OC the heck out of your current processor and run sli, because you do have x16 pci-e slots. But your bottleneck (while not too bad) would simply be the other direction, the cpu. But I didn't list this option because you mentioned being uncomfortable OCing.
I must stress that my post is ONLY my opinion/suggestion. Do whatever makes you happy. I do firmly believe after much personal testing, and way too many websites agreeing, that x8 pci-e slots bottleneck higher-end gpu is unfortunately, a fact. And is not an opinion.
If your wondering, hey Wickedsnow, what would you do in my situation? I would say.....
Buy 2 570SC's and run them in sli on your current setup. if your running a single 1080p monitor, then your bottleneck wont be too bad. Save the money that you planned on using for an i7-950 with new corsair dom. ram and the rampage 3, put it aside until later this year when the new sandybridge cpu's are available. (which is rumored for sept - october this year)
Whatever you decide on doing, just make sure that you confident and happy about it. If you even have a small doubt about anything, don't spend your cash and do more research.
Have a great day man!