I would say a newer, cheaper system would be a better buy. Heck you can build a pretty nice machine for $500 in my experience.

Yeah, I'd agree upon building a system. $500 will get you some nice older parts. Heck, $500 might net you a nice, G3258-based system if you want to go that route.

1 place I work has a few T5500's running as low priority servers (like CCTV server) Really well built and reliable. Keeping my eye on them and hoping to get one when they get replaced.
But wouldn't actually pay for one, much better deals out there

I bought a used ex-corporate T3500 for a little more than $100 on ebay. It came with no OS nor a even a COA. I pulled the HDD and swapped in a 120gb SSD and 3tb HDD. Installed a dual-slot Radeon R9 280, which does JUST fit after removing some various brackets, I did have to install a 650 watt ASUS power supply as the Dell unit only had one 6-pin PCI-E connector and I needed a a 6 and 8-pin.

It's now running Windows 8.1 and runs fantastically, though I desperately need more RAM, 3gb is the smallest amount I've had in years, it'll take 24gb though. It plays every game I've thrown at it, Talos Principle for instance, though it's not a very demanding game. We'll see about GTA V, but that'll have to wait, I refuse to pay $60 for a game.