You'll get between 130-260mbit/s with 802.11n (dependent upon how the radios are used).
Currently i'm sat in the spare room/study with an 802.11n router downstairs and am getting an indicated 130mbit/s. It usually sits at that speed for the majority of the house and environs for me.
Certainly better than the earlier homeplugs for me for throughput. I'd get yourself an N-wifi irrespective of if you need it for video streaming, as it also makes websurfing page latency a lot nicer and is a good investment whatever the case
