I am currently using an E8400 CPU. My current motherboard is capable of being upgraded to a Q9650 at 3GHz. This quad CPU also has a 12MB cache. I am wondering if I should upgrade my CPU only, or if I should also upgrade my motherboard to enable the use of a core i7-950 at 3.06GHz. Would I notice any additional benifit, cosidering this CPU has a smaller 8MB cache?This PC will be mainly used for FSX.Any advice would be most appreciated!

Since you already have a decent CPU you'd want to step up to the i7 for sure.If you overclock your current CPU to 3.8-4.0Ghz it would give you a nice boost.You'll want to spend the extra cash to get a i7 930 or 950 and overclock that to 4.0GHz

The Q9650 is still a beast. i7 is going to be $250 + 200 for a new MB. The q9650 is still at $330 because it still holds its own against the i7's. i7's have Hyperthreading now which FSX doesnt utilize. If it was me, I would go q9650 and some low latency high speed ram. Save the i7 thought for your next complete build. The i7 still needs and good MB to utilize it.

If you want to run heavy add-ons go straight for the i7, the Q9650 will only get you so far. Gigabyte mobo's are good and a tad cheaper. The Q9650 may not always overclock easily, mine didn't. And the i7 950 have become pretty cheap now. I'm making the switch myself these days, can't wait for a smooth ride in ORBX-world + REX2.

All other things benig equal is the i7 faster (better fps) than an Q9650 as the i7-950 has ony 8MB of cache? I also wish to use multiple monitors and perhaps a second graphics card. If I was to go with an i7 which Gigabyte motherboard would be best for FSX?

Before this goes any longer, what mother board are you using?? Because if your not using a high end LGA 775 MB then you will be wasting all the power that the q9650 can offer. If you are stuck using 1300Mhz DDR2 Ram then I would say go get the i7 and a new MB and use DDR3.

Hondabuff, I am using a Gigabyte EP35-DS3P. Max ram speed is DDR2 1200 if I overclock. This motherboard can take a Q9650 and the FSB can overclock to 1600

Don't know about the cache size, it's just the shared experience from fellow ORBX users that point out that i7 gets your sliders up. And yes, you need new mobo and ram. On your current rig you would have to overclock your ram at the expence of higher CAS latency and the risk of frying them. So, for a new Q9650 overclocked it would be a shame to have the ram as bottleneck. So you should calculate with a new set of ram too. Expenses seem to rise, and the most sensible thing would be to save up and invest in current generation hardware. My 2 cents.