Not sure if you've already gotten everything, but meh. Without knowing the actual pricing on parts in your part of the world, the three things I'd say you could dump a little more money would be: the graphics card (getting something like a GTX 460 or Radeon 6870 or 5870 [the 5870 is the more powerful card while the 6870 is more efficient and still more powerful than the 5770] if it fits in your budget would beef up your gaming abilities), the processor (if you get lucky with that dual core you may end up with a quad core, but it'd be safer to spend the extra money to ensure that you get a quad core, though it's your choice and the dual core may be just fine for you, I don't know) or the case. The case is the weakest argument, especially with a not very high end build, but something like the Cooler Master HAF 922 might be a little easier to build in/make the build and/or taking care of the system a little easier, though, as I said, that's definitely the weakest argument of the three.
You could spend more on the PSU, but 520W should be suitable for what you want to do (even if you unlock two extra cores on that processor) and you'd probably prefer more money to give more performance or more ease/certainty.