I have 3 Fujitsu Esprimo E900 midi desktops for sale, £150 each.
They have an i5-2500 @ 3.3GHz CPU, 4Gb of RAM, a 500Gb SATA HDD and a CD/DVD writer. Inside I think it has 6 SATA ports, space for a 2nd HDD and an NVidia Quadro NVS 300 video card installed (there's also the built in vid card...