You don't need Z68, you have no SSD and already have a video card. You can get a P67. And most important get a mobo where the VRMs have heatsinks on them, your model doesn't have them, you can go look for something like P8P67, forget the LX, LE, whatever skimped on, versions. Get something with cooled VRMs, they will be important for your overclocking. And welcome.
Z68 are well worthwhile, but P67 are very good as well, and usually quite a bit cheaper. If you wanted to go Z68 thats fine, but at least for the Asus ones go with Z68-V or V pro, not the skimped on LX-LE ones, less chance of having good overclocks, they dont use storage performance as well, and the heatsinks and such are way not as good, they are very skimped on.
Also for Video card, I have a 6870 and even though I can overclock it very high with a custom cooler, it still cannot match a stock clocked Radeon 6950, so for me it just makes more sence to go with a Radeon 6950 as oyu get more for your $. I have a few friends that got the XFX 6950 2gb/1gb models with the dual fan cooler, or the XXX which is a factory overclocked to 830 on the core, and they all love em, they get at minimum 20FPS more then I do with my overclocked 6870, price difference of around $50, if you overclock it(easily done) it can get some 30+fps minimum boost over a severely overclocked 6870 and can match a 6970 in performance, anyways thats my recomendation XFX XXX 6950 2gb Dual fan cooler model, they really are amazing cards.
I would also go for an SSD if you can afford to do so, newegg is having a sale on SSD right now for 15% off with coupon code BLKNOVSSD for Vertx 3 and Agility 3
As for rame G.Skill Sniper SE, G.Skill RipJawX or Corsair Vengeance, I have RipjawX which are deisgned around Intel P67 and they work wonderfully and are very overclock freindly, mine are 1866mhz 9,10,9,28 I have running 1866 9,9,9,24 at 1.501 volts, and they are quite low profile which helps, I use Hyper 212+ cooler with 2 of the bladmaster 76.8cfm fans, keeps my Phenom II x4 955 happy and cool :)
you are getting a 2500K and they run very cool even over clocked. Just get the hyper 212 plus, they are cheap and are very very very good. You would perhaps see maybe 1-4 degrees difference than a H100, but the price difference is too high.
Birk, if you looked at the links, you'd know they're in Australia, so I'm not going to ship 'em in just for a tiny bit difference. So I'll go with the Coolermaster Hyper-212+, though, I'm wondering if my PSU is enough :/