1) Yes...it's a reasonable spec, although the CPU isn't the latest in terms of capability. Either swap for an i5-2500K, or wait for Bulldozer. It depends on your budget (you've said how much your system costs, how much do you have to spend?)
2) It's a good build...it's really up to you to determine if it's good for the price. Try the same build at different online stores and see how the prices vary.
3) I'd go to 4GB of RAM, you won't need more than that right now for gaming and you can easily upgrade later on. Corsair Vengeance RAM is cheaper (at least in the UK, not sure about where you are) and more or less the same capability - certainly, you won't notice a difference. Also, swap out the Corsair PSU for an XFX one. I was given that advice and it saved me about £15. They're the same inside. If you can, get a 560Ti...it's pricier, but a very good graphics card for a gaming system right now. If gaming is your focus, you don't want to cop out there.
If its a gaming build the GPU is by far the weakest part, I suggest you get a better graphics card even if it means you drop the CPU to an Athlon x3. I don't know how much that motherboard is but unless its very cheap I suggest a 9XX series for upgrade-ability in terms of CPU and supporting SLi if you stay with Nvidia.