Considering future upgrade. ?'s and Opinions Intel Core 2 Quad Q6600?

Hi, considering a CPU upgrade in the future if I can snag the chip $100 or less (new or used), even if I have to wait a while to find one at that price, so I have questions and am looking for suggestions as to which chips to keep an eye on and what the possible performance gains would be of said chips.

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Vista x64 (waiting for Windows 7)
Asus P5W-DH-Deluxe -link
E6600 Core 2 Duo @ 2.40 GHz
8GB DDR2 800 Memory
650W Corsair PSU
3x SATA 3Gb/s Disks
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Sapphire ATI Radeon x1950xt 512MB (This is getting upgraded, new card is in the mail)
New Video Card (EVGA GeForce GTX 260 Core 216 Superclocked Edition 896MB)
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My current MOBO supports C2Q processors but it runs at 1066MHz FSB.

I've seen nice options like the 1066MHz FSB Q6600 as well others that run naturally at a higher FSB 1333. I'm not sure what would be most powerful for me, but a few options would be good and I'll try to snipe a good deal.

I do run software that supports 4 Cores and I do tend to have a LOT of light and heavy duty apps open at once, however those programs aren't running slow as it is so atm more power isn't actually an issue. This is a more forward thinking upgrade, as to how long it could possibly extend the life of my current build into the future.

All opinions and suggestions are greatly appreciated. Thank you very much for your time. -Derek

That's an amazing link you gave me, thank you. Your suggestions on which chips to go for are also incredibly valuable to me.

The only question I have left for you is, is it worth it? What kind of benefits would I see from the Q9550 over my current setup? I'm not quite sure what this upgrade would do for me, which would determine what I'm willing to pay for it.

At any rate, thank you so much gk.

45nm cpu support

I would stick with q6600, q6700.

EDIT: Dint refresh before posting...

Even I just went through the problems using the Q9XXX series on that mobo...
Seems better off getting the Q6XXX series...In that case, the Q6600 is the best option...or you can also check out the Q6700

But apart from a slight hit in the speed, the Q9550 does work with that mobo...So I would still suggest that Q9550...Better manufacturing process, and the large cache would still be helpful...
But it is upto you to choose which one to go with...
Looking from the complete compatibility perspective, even I wouldn't suggest the Q9550...But it works...

Q9550 would only work @2.26

I'm currently running a Q6600, have been for over 2 years. It's a powerful processor even at stock. I don't foresee myself upgrading anytime soon. Overclocks very well also.

^ A upgrade from E6600 to a Q6600 is a good upgrade as you have said that the apps you use do take advantage of the multiple threads...
Though there are newer CPUs soon to be release, you would have to change the whole setup(Mobo & RAM)...If you are OK with changing the complete setup, then wait else go ahead and get the Q6600 before even they become scarce...

Look around. I was able to find a brand new Q6700 for $175 at Ewiz, but I got the last one. I really didnt want to spend that much on a older 65nm processor but thats the fastest chip my mobo would support. I see some bidding around $130 on ebay too.
You may want to look into a P2 940 and mobo combo. They go on sale from time to time. A few weeks back Newegg had the 940 with a free 790GX mobo.
Ewiz has the P2 940 for $166. Going that route would also give you an upgrade path.

I would just wait till you have the money to upgrade the ram, cpu, and motherboard. Sticking more money into such an old board/platform does not make much sense. I would save up for i7 or AM3. i5 might be an option too for you in the near future. If you feel you have to upgrade now, I would go with an AM2+ motherboard and a Phenom II.