ARC REF 150SE vs REF 160S

I can’t say but I will have the same preamp (I demoed a Ref 6 and was sold) driving my Vandersteen M5-HPAs which are hooked up to my 5A Carbons. If I were you I’d audition the M5-HPAs. 

I have basically done the same had Vandy 2s upgraded to Quatros and went from Rogue Cronus to Aesthetix Atlas and Pallene
when I was thinking of making the change amp or speakers I ask Richard he said if the front end is good then the biggest change is going to come from the speakers both are great amps but maybe a pair of Sevens or Ref160 monos that is how got Quatros before the Aesthetixs

Enjoy the Music
Tom

I moved from the Ref 150 to Ref 150 with KT 150s which ARC reps told me was almost as good as the Ref 150se. Then I moved up to Ref160 monos. There was a difference between my Ref 150 with KT150s and the Ref 160 monos but it was maybe 15 percent for twice the price. I assume the Ref 160s would be in the range of 10 to 12 percent better than your amp. It will be a noticeable difference but not a huge difference.
But when you move up from the fabulous Ref 150 to any amp in that power range, you reach the point of diminishing returns. 
The the price for the improvement is dear and not  mathematically proportionate to the gains.  Would I do it again? Hell yes.

@gpgr4blu  You bring up an interesting point. When was it that any gear manufacturer stated that their latest and greatest, which now costs 2-3X the last product, was in fact only 'maybe 15 percent' better? I can not recall one instance of this...
To that, there are many well known examples of gear that was replaced with the 'latest and greatest' that is in fact inferior to what it is replacing- and sometimes by several degrees!  Not once was the price lowered though with the new introduction. Pays to listen to all new gear in consideration before a purchase, and not go by the 'hype' that inevitably is attached to it, IMHO.