Now I'm sticking with Dell, we've bought lots of refurb Dell machines (as in probably 4 in the last 5 years) with nary a problem (dumping wine on the laptop doesn't count), and we're a Dell shop at work, so I've got good communications with sales and support.
Likely the machine will be a Dimension 5100c or XPS200 (which looks a lot like the 5100c rebranded, neh?). Yeah, the small form-factor is a big deal to me (what with already not enough space on the desk). Pentium D 820 (dual-core 2.8ghz) processor is high on the list of wants, along with a DVD burner.
The big question that follows that is: What do we do with the old machine? It might be fun to throw up a linux box again, so if anybody has opinions on linux distributions, I'd like to hear them. I've done SUSE, and would consider doing it again, but Fedora is mighty tempting. The old machine is much less wonky than the previous no-name celeron box, so it should be easier and more reliable.