I have the same motherboard and processor in my current HTPC :-)
I'm not sure you need the geforce 8400...the 780G is plenty fast for HTPC duty.
Also consider the Fusion HDTV tuner if you really don't need one that support CableCard for your Verizon FIOS:
http://www.digitalconnection.com/Pro.../fusion7rt.asp
or the HDHomeRun:
http://www.amazon.com/gp/product/B0010Y414Q
Both work well w/ MythTV on Linux.