I know this is old school hardware, which desktop to keep and squeeze out the best video performance.....?

The Sony. I had a system like that Vaio, and it ran til its proverbial feet fell off. As far as graphics, what you're gonna want to do is get an AGP slot graphics card (The ATI all in wonders are pretty great for that) But regardless of which one you choose, you wont be able to run any newer games requiring newer DirectX software. If you have the means, Just look at barebones systems, or even lower end new computers. Acer makes some GREAT products for around $300.