This will probably sound a bit strange to many, but I've lately taken to buying refurbished Dell precision T3500 Workstation Windows 7 boxes off of Amazon. For around $250 I get around a 2.5 Ghz Xeon chip & 12 gigs of memory. The box only supports 24 gigs, so I max the memory, throw in a better video card (particularly if it's a video editing box) and for around 500 - 600 bucks have a workhorse full desktop that's easily upgradeable.
My studio is running one now (with another hot swap spare sitting in the wings since they're so cheap). Haven't had any reliability issues from it being a refurb. For the classic rock oriented studio stuff I do (Cubase Pro), I'm not running 500 track sessions, so I can load SSL strips on every channel plus all the other plugins I need, and it's never squeaked once.
Full disclosure, I'm a professional geek, so I'm comfortable with this sort of thing. That said, if you're okay with replacing some swap out components, this concept is certainly high in the bang for the buck category.
Thank you, Chris. That's pretty resourceful and if I were a bit more proficient in that area I'd really consider it but now I think I'm looking for something out of the box.