i did a bit of research on this before i built mine and i found that the j1800 on that board struggled with media at 1080p you have to go to the top end of them boards for them to become useful for a htpc. In the end i went with the Amd Am1 route
Just to give a differing view here, I have the Gigabyte GA-J1800N-D2H running Win 8.1 and XBMC and it copes with 1080p MKV files (some 20GB+) played from a NAS perfectly well.
Spec:
Board: Gigabyte GA-J1800N-D2H
RAM: 4GB SODIMM
HDD: 40GB Intel SSD
Case: In-Win BM639
OS: Win 8.1
Set to start XBMC straight after boot and added the Netflix Chrome Browser addon which runs perfectly well. For just under £44 this board is a steal