First off, welcome to GN! We love helping out with these kinds of builds and you have selected some very nice components! Thanks for the detailed post also, that helps the process a bunch.
As I said before, you selected quality components for sure. I would suggest that you combo up the parts. The I5 2500k can usually be in a combo with an ASRock Z69 or even a Z77 if you can afford it. Since you mentioned upgrading in the future and overclocking you might want to look into getting the Z77. Then I would def combo the Thor case (great case BTW) with a rosewill Hive PSU, probably the 650w since the 550w is sold out. This will save you a good bit. Then combo up the video card and RAM, saving more!
If you really are going to overclock, you really should get an aftermarket heatsink for your cpu. The I5 2500k is made to overclock, and the after market heatsink will keep them temps down allowing you to push it more. The Thor is a big case and should have no trouble housing the bigger heatsinks.
If you are looking for a true gaming mouse I wouldnt get the Xornet, I have it and the buttons cannot be programmed like a true gaming mouse. Maybe look into the Razor Naga, it costs more but is really worth it.
You are right on with the SSD, you could put the OS and a few games on it and wait out the HDD prices. Well done there.
No real complaints anywhere, you have a good rig set up there. If you could, I would use the combo savings to get the best GPU that you can afford. The 6950 is a good card, but this is a gaming rig, so throw the best GPU you can in it. The CPU will most likely hold you over a few years at the least, Sandy Bridge CPUs perform very well. So the spot I see for improvement if possible would have to be the video card and/or RAM to 16gb. I will post some combos below to give you an idea of how much more you would save to upgrade if you want. If not, the 6950 is a good card. You really can't lose out either way. Since you do not plan on crossfirex or sli, get the best GPU you can now.
Case/PSU combo
Thor and Hive 650w
CPU/Mobo combo
I5 2500k and ASRock Z68
GPU/Ram combo
6950 and Corsair 8GB (couldnt find the same RAM you linked, but very similar quality RAM)
Heatsink
Tuniq Tower 120 This will help keep them temps down and provide you with a much better overclocking experience. It is good quality, and we have tested it and can vouch for it's performance. (so all you other companies send us your items to test lol)
I like the SSD you linked, but we love the
Kingston HyperX 3k. We tested it in house and it really performed well.
Let me know what you think, and we can make any adjustments you might want. If the combos free up any room to upgrade anything or not.