You might be able to put a AM3 socket motherboard in there, you would have to make sure though that the case has a removable back plate because in alot of those proprietary cases they have it physically built into the case which means you would have to cut it out with tinsnips or use the exact same motherboard.
This is good quality:
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=6321553&CatId=5539
and it has 4 ram slots for your case.
Otherwise i would stay away from biostar ive had them in the past and i dont trust the quality of those. 3 motherboards went out that ive had from them and the warranties on them suck.