I spent a few hundred dollars on a dell optiplex 7040. Has an older i5 quad core, 16GB RAM and a 2TB SSD.

Has no issues running start9, full node and my public-pool instance.

Just make sure you download the right start9 OS version (x86_64-nonfree.iso) as it'll have more drivers and the like. I used the wrong one and my wireless adapter wouldn't work. No biggy...just went with ethernet anyway.