Can't say much between the Usher and ProAc...never heard the Proac. Just writing to say that the Ushers work very well in my room that is of similar proportions...12 x 16. 200 watts is also very good...they need lots of power...I run 200 watts and it is night and day compared to previously using 125 watt amp. I am curious about more, but I have heard enough systems to know 200 is close to right for these guys.
