Wow you picked a hell of a board! I have found the S5520Sc to be very difficult to work with.
Anyways I have successfully used a ATI 4890 PCI-E.
Trying to quiet down the fans in Chenbro 105 case with that motherboard - and so far no luck. I have yet to "meet" a moodier, quirkier, more difficult motherboard to work with - and I've "met" a few. Not marrying this one, sorry. Took me 4 hours to figure out how to flash the BIOS.
I've tested it with Quadro FX 540 and 1800 - those do work. Try disabling NIC EPROMs (in PCI devices) and see if that helps with the "not enough resources" issue.