Very nice system, speakers. This is a very exciting question. Audio Research with Sonus Faber is magical!
It would be great to see your system as it is today. Makes it much easier to make relevant comments. There is a place under virtual systems to post photos and ID your equipment.
Lots to consider. I have had both the Audio Research Reference 160m monoblocks and the Reference 160s for over three years, and I run Sonus Faber Amati Traditional. The monoblocks throw a deeper and wider sound stage. They are a must for the mix.
I would definitely use all Audio Research amps. You do not want to combine amps with different character, that would be a horrible thing to do. Obviously the ideal would be three sets of REF160, monoblocks. That would simply be amazing. Just the thought is so amazing… if you can afford it… simple talk directly to audio research about the ideal combo… well, do that under all circumstances.
Talk to ARC… but you might end up with a REF80 for the high frequency, REF160m monoblocks for the midrange and use your REF 160s for the bass. If that is too expensive… maybe just Biamp? use your REF 160 for the bass and add monoblocks for your mid/upper range. My feeling is this last combo would get you the extended sound field and much more punch and clarity.
Also, Audio Research will be releasing their Referece 320 amp soon, this might play into the picture.
Where do you live… I’d love to hear your system before and after. I live outside of Portland, OR.