MC75 in Bi-Amp Vs MC611 to drive Amati Tradition

Hi all,
Got the itch to upgrade soon, my system as follows; MC75 MKIII monoblocks, C22 pre, Sonus Faber Guarneri Evolution. I realized that my speakers are too small for my 9 X 5.5 m / 29 X 18 ft room, considering that I booked a pair of new Sonus Faber Amati Tradition and another pair of new old stock MC75 MKIII monoblocks.

However, after I researched more about bi amping it seems that some feels it is one of the best upgrade and some feels it doesn’t have any effect on the sound/total waste of money. With that in mind, and considering that I can still change my purchase with the dealer, now I also consider MC611 instead of bi amping the MC75 to drive the Amati.

What would be the best scenario to drive the Amati? Speakers specifications said 100-500W recommended power with 90db sensitivity, I know a pair of MC75 alone without bi amping will drive the Amati but not optimally. Going MC75 on bi amp will also end up costing more than MC611 due to dual interconnect and dual speaker cable needed to run bi amp so if the sound will be inferior than MC611 it will be not worth it at all. I like tube gear sound the most but I heard new Mcintosh SS are very tube sounding. 
Thanks in advance peeps!!

PS: please do not suggest other amp other than Mcintosh. Not brand fanatic but it’s the only brand which I already have good relationships with the dealer and yes the fact is I like Mcintosh