New cheap gaming build

Looks fairly good, but a few things that I should point out:

1. Your PSU (and your mobo) will not allow you to XFire, and the 5770 isn't very strong when enabling DX11 (as seen in Dirt 2). If you could swing it I'd highly suggest a 5850 now. If you can't then you'll probably have to upgrade in the next few years. You could also go crossfire but you'd need to change you PSU (700W+) and your mobo (I suggest ASUS P7P55D-E Pro). Note, this changes WILL increase the price of your rig.

2. If you plan on overclocking the stock cooler won't be enough. I suggest the Cooler Master Hyper 212 (which is only about $30US) but it is not necessary if you're not OCing.

3. Caviar Blue drives are WD's "mainstream" drives, which means they don't operate as fast as some other "high end" drives. Samsung F3 Spinpoint, Seagate 7200.12, and WD Caviar Black 2TB are all "high end" drives which have 500GB platter designs to give them a higher throughput. If you can find one I suggest the F3 Spinpoint as it generally seems to be cheaper on this side of the waters.

As for your questions, this rig looks great for right now. The only thing that would hold it back is the GPU, which can be fixed in the options above. Don't get me wrong, the 5770 is a good card, but probably a year from now you'll be wanting more power, at which point you can easily do a GPU upgrade.

Finally, I know you mentioned you didn't want to build it, but if you have the time, I suggest you build it yourself. It's really quite easy and there are guides all over the internet that can help you. The two big benefits from building it yourself are that first and foremost, you save money. You don't have to pay some hardware schmuck to do the work for you. Also, you become more intimate with your rig because you want to place every piece with care. It's something that is completely yours.

Anyways, hope this helps, and whatever you choose goodluck and have fun.

Oh yes, for what you need to do it will do you quite well for your needs.