Ditto to the response from Estegall. I have the 6381 and was initially introduced to the 6311's, but preferred the additional bass extension on the 6381's. Incredible build and quality finish on this speaker line. I've been hard pressed to find as satisfying a listening experience with other brands I've heard.
Lately, I impulsively purchased a beautiful pair of Kef XQ5's at a discounted closeout price and am playing this with a CJ-MV60SE/PV14L2 tube set, however I'm missing the broader soundstage and bass extension of the Ushers. Unfortunately I'm too lazy to swap the speakers to see for myself as the Ushers are sooo heavy, and I'm hesitant to potentially mar the black lacquer finish if I try to move them around the house.
As customary for this audiophilic syndrome, I lately lucked out on a mint Cayin TA30 on Audiogon for my loft/work area of the house, and discovered the Usher S520 monitors to mate them with --these little Ushers are just as amazing and surprising; they blew me away when I heard the music that just flowed out of them for the size and the price that they are selling for - check out the reviews. So overall, I've become a fan of the Usher line, and am even considering trading in my Kef's (had them just for a few months) or selling them on Audiogon so I might get a pair of the 6311's or 6371's. Good luck, with your search but do listen before you buy, as we all have our own preferences for music and how its conveyed.
Joe