Focal/JM Labs Nova Utopia Be

I'm going to be acquiring these speakers next week as replacement to my Dynaudio Countour S3.4s (a significant upgrade to say the least). Provided the size of the speaker and the low frequency response, I am wondering if any owners or previous owners of similar speakers have experienced any difficulties incorporating beasts such as these into a moderately sized room. My system resides in a 20' x 13' room with the speakers/electronics along the short wall. The corners, first reflection points and rear walls are acoustically treated. Additionaly, the stated nominal impedence is 8 ohms with the minimal impedence dipping to 3.6 . Would it be advisable to utilize to 4 ohm taps of my Mac amp rather than the 8s? Thanks in advance. New speakers is always both an exiciting and daunting venture...