No offense Dronks, but those builds could use some work. If you look around for good combos, you can save quite a bit of money.
I would highly recommend not skimping on a case (but that doesn't mean you have to get a $100+ case), as working in one will be a nightmare, and you could possibly hurt yourself (sharp corners). For low budgets, I'd recommend a HAF 912.
The motherboard is a mircoATX form factor, which usually lack a lot of the features that are semi-standard on ATX motherboards. Unless you're doing a specialty build (that requires a small form factor), I would stay away from mATX boards for now.
The graphics card is pretty decent, but you can get a GTS 450 1GB for around $115, which isn't too much worse, or even get a 460 768MB for around $150 which is a lot better. I wouldn't really recommend the 5770 anymore, unless you are on a
very strict budget.
The power supply is a good choice, but this system wouldn't need more than a CX430 or similar. Because of the low cost and the decent looks (I just did a build with one not too long ago), I'd go with the CX430 over other ~400W units.
Depending on what games you play, the Athlon II 400 series is a better choice because it has more cores, and not every Phenom II 500 series is guaranteed to overclock, and who's to say the VRMs could even handle it? But, if most games only use one or two cores, then might as well go with the Phenom II 500 series.
That ram seems a tad overpriced to. Unless you're going to be setting benchmark records, getting more than just some 'normal' memory sticks isn't needed, and won't cost more than $45 (since the last time I checked).
Just some thoughts. I'll do a build and edit it into this post.
/E Here is the build.
I actually go manage to get a Phenom II 820 and a GTX 460 in there, while staying under $580. If you need an OS, then I might be able to get you a legit copy of Windows 7 Pro. Big maybe. PM me if you need it. Here is the build.