Which SFF Motherboard will fit?

Hi,

I've a Biostar iDeq 330N that is feeling the strain of modern living. Can anyone suggest a modern small form factor motherboard I could replace the OEM C51MCP51 with? Preferably quad core Intel/AMD with integrated sound and video although I'm happy to fit a suitable video card if not. I'm no gamer but I do [try to] stream and watch videos (mp4, swf, etc) and when I'm surfing I have many windows/tabs open.

I've lost touch with modern developments so any help you can give me will be greatly appreciated.

Thanks

 

I'm not sure about the C51CP51 motherboard reference. This is what Belarc Adviser and CPU-Z says it is but from what I can see the motherboard is not a MicroATX. Not sure what form factor it is now!