A few years ago, I collected a bunch of basic Dell servers (because they were almost free). Stacked them full of disks and have been using them since. Of course, like most machines with moving parts, the power supplies and fans start failing after awhile (taking your whole server along with them). I'm too cheap to replace them with $1000+ servers that use the same amount of power. Of course, you can buy a new server that uses twice as much power for less than that.
The problem with basic Dell servers (like the 600SC) is that they have proprietary fans, which are very expensive to replace. The 600SC's motherboard won't boot unattended unless you plug these fans in.
So as a compromise, I've bought some Antec Sonata cases and plugged in the old Dell parts, and they work, at 1/4 the noise level. I can't do automatic reboots (have to hit a key) but that happens only once every 6 months anyway.
One of the challenging bits: on my most recent attempt, I learned that the 600SC's motherboard has a proprietary heatsink for the CPU. The motherboard tray has special holes for just this heatsink. So what to do?
It turns out that you can take some motherboard risers and snip the screws off the bottom (Lorna took a class involving metalworking, so we have all this equipment). Once you do that, it's easy to attach the heatsink. Remove the peripheral cutout, and things are working again.