The Mobile Option: ASUS Eee PC 1215N
On the outside, the ASUS Eee PC 1215N is a very nice little netbook. It has a 12.1" display, a surprisingly pleasant and spacious keyboard, and a touchpad that is also quite large for the laptop's size. It's a bit thick for a modern netbook, but that's more of a nitpick than anything.
Once you dive into the internal specs, however, you'll see why it's the best gaming pc under 500 bucks in the mobile category; it's virtually the same has the Verition. The Eee PC 1215N also has Ion graphics, and also has an Intel Atom dual-core processor. It even has the same amount of RAM (2GB) as the Verition, although the hard drive is a little smaller.
Honestly, if you're really this budget restricted but need a gaming PC, you may as well buy the ASUS Eee PC 1215N. It's every bit as fast as the Veriton, but you can take it with you when you leave home.
The Budget-Stretching Option: If you're able to find an extra $100 somewhere you'll be able to afford a much faster laptop, such as the Acer Aspire AS5742G, which has an Intel Core i3 processor and a Nvidia GT 540M graphics processor. This system is several times more powerful than the ASUS Eee PC 1215N, but costs just $120 more.