No, this model cannot support Intel Pentium 631 CPU. This model support Core™2 Quad*/Core™2 Duo/ Pentium® Dual Core/ Celeron® Dual Core/ Celeron® 400 series processors. The following website is the CPU support table for your reference.
http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?DetailID=1093&CategoryID=1&MenuID=16&LanID=0#Fragment-CPU

Due to the Intel G41 chipset spec, this model runs at DDR3 1066/800MHz memory speed, though BIOS setting, it can over clock to DDR3 1220MHz when using DDR3 1333MHz SDRAM with FSB 1066MHZ CPU. Due to Intel E5800 CPU is FSB 800MHz CPU, it needs to update FSB 1066/1333MHz CPU to over clock memory speed to 1220MHz.

Yes, this model can support Intel Q8400 CPU. We strongly recommend users to use the CPUs listed in the CPU support table we tested and qualified.

Yes, this model can support Nvidia XFX GT9600 graphics. The below graphics table listed the graphics we tested and qualified for your reference.

This motherboard comes with VIA® VT1705 HD 6-channel audio CODEC. The front audio header allows the user to install auxiliary front orignted microphone and line out ports for easier access. Please refer to the front audio pin definition.