Advanced format drives have 4k sectors, and shouldn't be used in Windows Home Server without using a tool which allows aligning partitions properly (and probably not at all for the system drive).
Most manufacturers publish product data sheets that list the native sector size for drives; have you looked for one on the Seagate site? That would be the best (fastest) way to answer your question...
I'll also note that you could buy a somewhat cheaper SATA II drive; there is no hard drive today with actual mechanical components that will benefit from the extra speed of SATA III.
I'm not on the WHS team, I just post a lot. :)