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 
uwiikz
A bigger Mac tube amp, maybe?
Getting bigger MC2301 seems like a logical choice but my dealer advised me against it although he will make more money if I buy the MC2301. He said the price of Mc2301 is not worth it if I already own MC75. FWIW he also did not advise me to get MC611 either, that was my own thinking. My dealer insisted that I will be happier with a couple more MC75 and bi amping. 
My main concern is if MC75 in bi amp config would drive Amati sufficiently. I just bought Transparent Ultra Gen5 XLR and already eyeing Transparent Reference speaker cable, meaning the total cost of extra identical cable itself would be morr than the MC75. With that in mind the result have to be worth it, hence my hesitancy.