Okay, this build is not exactly a thing of beauty, but it gives you:
1) AM3 Mobo
2) AM3 CPU
3) DDR3 RAM
4) You can build on the RAM and the Mobo. If you want to later, just drop in a better CPU and upgrade the GPU, PSU and perhaps the case.
1) The hard drive is just barely big enough and it's kinda slow, but it shouldn't effect your overall performance too much.
2) The case is not great, but it's cheap and hopefully a decent starter
3) The CPU is not a beast, but it's a dual core AM3 with good clock speed out of the box, and maybe you can do a MILD OC on the stock cooler, and get it up to 3.0 ghz or a little higher.
Although with no fans included in this case, OC'ing is probably not a good idea. That CPU should be fine on it's stock settings. You may want to look into ordering a couple case fans in the near future. They're pretty cheap, and they're worth their weight in gold since they help keep your system cool, and cool systems run better and live longer This case can hold 2 120mm fans and a 80mm fan BTW.
4) The graphics card is not a beast either, but it should play games at low/medium settings at your resolution. Maybe at medium settings...
Hope this is helpful, and maybe some more experienced members will offer some input on this build or improve on it with another. This is about as good as you will come up with performance-wise at this price point.
*I love doing hypothetical builds on Newegg *
* I wish I could do that for a living...*
If you don't need an OS, or you can re-use other parts, I would use those extra funds to upgrade the graphics card and CPU first and foremost, next in line would be upgrading the case, and lastly, depending on the card you get, you may need to upgrade the power supply. For $12 more, you could also get a nice 500GB Samsung Spinpoint F3 hard drive.
Or, better yet, if you don't need an OS, here is a build that comes in at $526.34--$35 in rebates= ~ $491
And it is DRAMATICALLY better than the one listed above:
MUCH better CPU (for everything but gaming, it's pretty even with the 240 in games), PSU, case, hard drive and graphics card with this build.
That's the power of an extra $100 when you're talking about a budget build
Personally, I would go with the 5670 GPU simply because it runs cooler and drains
less energy. Plus, it performs relatively close to a 4770 and would be a dramatic improvement
over the 4550 listed above.
If you wanted a good budget gaming PC I would save up another 100-200 more because your at a point where that amount of money can more than double what you get if you look for the deals. Take a look at the tower I built on this forum and take a look at the price and how much more it offers for the $100-200 more, its cheaper in the long run to just save up a bit more in my opinion.