Hey man, looks like a pretty solid setup. I won't comment on the hardware as it seems you've made up your mind (although that PSU is overkill =P), but I'll give ya a couple tips for testing components once you've got it up and running:
GPU: I doubt it will be an issue since you have one that I assume works as it should, but you can use Furmark to test if it will fail under load. Just watch the temps and stop the program if they get too high. If Furmark runs stable for 10 minutes you are most likely good.
For testing your CPU and RAM I use Prime 95. Again, watch the temps and start with a lower number of threads running (say 5) which should be sufficient to test the components anyways. Here is a forum discussing using Prime95 if you are interested.
Try to test your components early so you can RMA them if they are junk. There's nothing worse than not finding a fault in the hardware until a few months later, and having to deal with the manufacturers warranty, rather than a simple return/replacement.
Definitely build your own, so much better than the prebuilt junk the retailers flog.
Have fun =)
Edit: could also get CPUid's Hardware Monitor as well, pretty handy to keep an eye on how your PC is running.
