Subwoofer for Vienna Acoustics Mozart Grand

REL has often been recommended with Viennas as well as Sonus Fabers. Maybe because of the Sumiko connection over the years but regardless, I believe there are many satisfied owners using this combination.
I use a REL T1 with my VA Bach Grands and couldn't be happier. The T1 is a fast, musical sub that syncs with my Bach Grands very well.

In HT applications, I agree that there are subwoofers that will go lower than a REL. The OP was asking about one that will perform well with his Viennas. As an owner of both Vienna and REL, I commented that this combo works good for me and many others. I stand by my claim that they are fast and musical subs.

I have a friend who has a Velo DD12 in his install. It si an awesome sub and extremely impressive when it comes to a movie soundtrack. But when we spin an LP or CD, my friend says he prefers my REL. Despite REL's unique connection, when time is taken to properly set one up, the results can be very satisfying.