Need Advice on buying a new computer

[Subnuts]

Hi everyone,
My current computer is an obsolete piece of sh*t, and I want to buy a new one. I can't even run DW on my current computer unless I turn off all of the graphics settings and play on the smaller scenarios. I don't need a monitor, printer, speakers, keyboard, etc., just a solid "box." I'm willing to spend up to $800 on a new machine, with the best possible processor, RAM, CD and DVD-ROM player, and graphics card that amount of money can buy. I don't need a bleeding edge gaming supercomputer, but I'd like one that could play SHIII and SHIV without any real snags. I'm rather computer illiterate, and have never bought my own computer, and was wondering if one of the "gurus" here could hold my hand and walk me through the process. Thanks!