So, you want a shell of a PC with no GPU or memory for $600 with a decent PSU and case?
For SLId 580s, you need solid PSU (check this link...http://www.slizone.com/object/slizone_build_psu.html).
3.3Ghz Intel Core i5-2500 6MB Cache Quad-Core
Stock Intel LGA1155 Heatsink and Fan
GIGABYTE GA-H67M-D2-B3 (Intel H67, HDMI, 2xPCI-E, 6xSATA, 2xDDR3)
500GB 7200RPM 16MB Cache Serial ATA300 (Major Brand)
22X LG SATA Dual Layer DVD+/-RW/CDRW w/Nero
Antec Black Nine Hundred (6 5.25, 6 3.5) 4 Fans, Audio/USB/1394
850watt Corsair CMPSU-850TX V2
Onboard LAN included
Onboard Sound included
Wires and Cables neatly tied up away from fans
3 Year Parts and Labor Limited Warranty
Probably the "least" you can go with from your desired site. Way more than $600.