Core2 Extreme QX9650 gaming?

Not work the money at all. You can get a cheap high clocked xeon lga 771 + a 771 to 775 sticker for around 30$. Also those will still bottleneck the hd 6870 in certain games. Also a pentium g4560 + cheap b250 motherboard and 8gb of ram is around 120$ and that thing just wipes the core 2 quads.

Is it a true QX9650 or is it a Xeon part with a soldering/pin mod? If it's the real deal I'd say it's not worth it in either case since the platfrom is already a pre Core i CPU part. Since it's conception, we've seen 6 generations come by. I own a Q9550 on an Asus Rampage Extreme X48 board and It's actually sitting in a closet since everything else(software's and games) have moved past it. In fact if it's for an office system, it's be pulling too much power to deem viable.

My vote=No. To quench my curiosity a little, what are your current full system's specs?

That's a tough choice, but for the money, the Q9550 is probably the better deal. If you can find one of the C2X CPUs for a good price then obviously go that route.

I would hold off and wait until you can save for newer kit. Both of those CPUs launched around 9 years ago.

You will need to check that your motherboard supports the Q9550 or QX9650.
However, its money down the drain as these are 9/10 year old cpu.

What is your motherboard?
Is it able to support either cpu.
Your Q8200 has a passmark rating of 2829 and a single thread rating of 993.
Not very good, and the single thread rating is what most games need.
The Q9950 has a rating of 4021 and 1201.
The X9650 is 4296 and 1261. Really not much better.

Really, I would not dump more into such an old platform.

I would like to humbly disagree with some of the other answers. While it is true that a G4560 build would be light years ahead in terms of tech and future upgradeability it would be substantially more than $120 to implement. Meanwhile the upgrade to the QX9650 has immediate, noticeable advantages.

Point 1: (per jaslion) Also a pentium g4560 + cheap b250 motherboard and 8gb of ram is around 120$ and that thing just wipes the core 2 quads.
Using pcpartspicker I see this build at closer to $185 (https://pcpartpicker.com/list/p74pNN)
CPU $75
Motherboard $47
RAM (1 8GB PC2133) $50
CPU Cooler $9
Thermal Paste $3
Total w/Tax and Shipping 185.39
After all that, CPUMark Score 5307
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Pentium+G4560+%40+3.50GHz&id=2925
The CPU cooler and paste is a must as the Socket 775 cooler is unlikely to fit an 1151 CPU.

Point 2: (Me) The upgrade to the QX9650 has immediate, noticeable advantages.
CPU $77
CPU Cooler $20ish (optional)
The advantages are not having to purchase a new Motherboard and RAM. Without knowing specs I would guess you have ~4gb of DDR2-800 RAM. SATA2 3GB/sec drive controllers, and a PCI-Express 1.1 bus for the graphics card. The PCI-Express bus is not slowing you down appreciably as the bandwidth of even 1.1 is more than adequate for your HD6850. The DDR2-800 RAM is about 3 times slower than new ddr4 (800/2133) and the QX9650 does not have a built-in memory controller instead it is a chip on the motherboard, so the RAM is definitely slower. Even so, DDR2-800 is dang fast and yours is already paid for! SATA 2 has 1/2 the bandwidth of SATA 3 however, your current HD is unlikely to be Faster than SATA 2, so SATA 3 does you no good unless you buy a new drive/drives, again price of new build rises.

Point3: Why the QX9650 instead of the 9550?
http://www.cpubenchmark.net/compare.php?cmp%5B%5D=1040&cmp%5B%5D=1047&cmp%5B%5D=1031
As the above comparison shows, your current CPU benches out about 2829, the Q9550 about 3637 and the QX9650 about 4246. The QX9650 however has an unlocked multiplier and If you invest $20ish in a better than stock tower CPU cooler you can Overclock it up to 3.5ghz just by upping the CPU multiplier in the BIOS and possibly adding .5mv in the CPU voltage adjust. then you are more in the range of:
http://www.cpubenchmark.net/overclocked_cpus.html Intel Core2 Extreme X9650 @ 3.00GHz 5,268

Now I will leave logic aside, having an Extreme Processor is cool, even a 10 year old one. mabye %1 of people have ever had an Intel Extreme CPU, come join the club. I have had my QX9650 to 3.75ghz on air though I backed it off to 3.5 just to have some margin, it is quite snappy. This is the 775 end of the line, your next CPU and mine will need to be i3, i5,i7 based but for now I think you would find the QX very adequate.

Good Luck and Good Gaming!

Your Motherboard does support the QX9650

https://www.asus.com/Motherboards/P5K_SE/HelpDesk_CPU/ though you may need to update your BIOS.

If your current ram is 2x2gb of DDR2-800 2x2GB you could add a set and have 8GB of RAM.
http://www.ebay.com/itm/like/151730669820?lpid=82&chn=ps&ul_noapp=true

$10ish

Xeons are the exact same cpus but with some minor differences that make them better at certain tasks.

The new pentuims essentially replace the i3's as they now have 2c+2t. They perform amazingly well for the money and will run every new game out now. If you do decide to get it do know that you gpu will then be whats holding your system back as these pentiums can handle a 1060 without bottlenecking it.

It's good that the gpu will hold you back because when you do get the c2q it will still hold it back in more cpu intensive games. With the pentium you have a future but when you get one of those overpriced c2q's you'll be stuck with it.

So my final advice is to save up a bit and get a pentium g4600 series + b250 motherboard + cheapest 8gb of ddr4.

The processor you're talking about upgrading to is only a small percentage faster than the one you have already. It's still going to bottleneck your GPU. Save up your money instead of spending it on things that will hardly improve your experience. Save up as much as you can for a year or longer and you will be able to buy something worth having. Until then enjoy what you have for what it is and not what you wish it was or hope that it could be. Play games that you know your system can run rather than being disappointed by what won't run. I personally save at least $30 a month for future CPU upgrades. It's well worth doing if you want to keep an up to date rig.