If you keep an eye on eBay, sometimes you can pick up a friend refurbished i5 system for not much more than that. In fact I was just looking and saw a Dell with an i5 2400, 4gb of ram, and no hard drive. However they had pics of bios etc. I think it was 105 with 20 bucks shipping, and was a mini tower, not the small form factor.
However, if you already have an old hard drive and ddr3 ram, you could upgrade the Dell. They said it has a Windows 7 product key. Which last I tried could still upgrade to Windows 10 free, at least the last system I tried a couple of weeks ago it still worked. So something like that might be worthwhile. You wouldn't be killing games, but you would probably get a lot better performance.
You could also check and see if your board can accept something like an old 960t zosma and overclock that.