Denon AVR 4306, Vienna Acoustic Baby grand Front

I don't know should I buy the Vienna Acoustic Baby grand (the same in my front) or the Sonus faber Cremona Auditor for my back speaker.
Please help
If budget allows and if the maufacuter makes a compete set of speakers built to work together, you show keep all of the speakers in the same family. Keeping them identical is even better.

Quite honestly, for movies, you may not notice a huge difference, however for multi-channel music it it important and will make a big difference.