camFreedom, liberty, equity and an Australian Republic
Dell makes all sorts of equipment. I've run RedHat on Dell Optiplex boxes for the last 11 years.
I assume this is for home, what's the intended application? If it's storage you don't need much CPU or memory.
Personally I'd build myself, using whatever parts they recommend in the current Tom's Hardware system builder guide.
If that's not your thing check out Dell/HP etc "small business servers", the prices aren't bad.
I'd check the Oracle minimum requirements, they're the kind of guys whose installers might refuse to work if they don't think there's enough memory etc.
If your time has no value you could buy a second-hand workstation. If $500 seems a reasonable budget you can probably catch the bottom-end Dell tower servers, sans OS, on sale.
As mentioned elsewhere, this is only a problem with video for linux. Even then, this typically means that it drops back to a dumb frame buffer and the screen refreshes .01sec later than it should, and 3d doesn't work. Which means your super-3d enhanced effects don't work. Or you can't play tux-racer and the two other linux games at full resolution. The difference between linux with "working drivers" and non-working drivers" can be pretty small. Unfortunately, I'm posting from one that I haven't gotten the onboard video to work right (it looks like bad palleting when it should be 24 bit) and have to use an ancient PCI board.
If my memories of that project are correct, I ordered it from Logic Supply: http://www.logicsupply.com/
If the xserve line wasn't so ridiculously expensive, I might consider going that route. But I don't have enough time in the day to fart around with Linux.
Someday, I want to visit a Fry's. Mostly this is an irrational urge that is a function of having come of age in the IT world while reading the Chaos Manor column in Byte.
"To this day that was the most bullshit caesar salad I have every experienced..." - triggerfinger
Of course, on that coast you can probably get delivery from newegg faster than you can get to fry's and back.