Charles1dad is correct. JA measured the Proacs sensitivity to be 85.5db. JA wrote: "The speaker's sensitivity on the HF axis (measured using B-weighted noise) was somewhat lower than specified, at 85.5dB/W/m vs 89dB/W/m." In my opinion, I would err on the side of more power, … not less.
And Adg101 makes an excellent point about "care and feeding" of the VT-200. If true, it appears that the VT-200 is a pain in the butt to bias. I surmise that blown bias resisters may be a major operation to replace if a power tube arcs, … and arcing power tubes just go with the territory.
The innards of my Ref 150SE are wide open. So if a bias resister blows, I don't need a neurosurgeon to replace it. And I check the bias on my power tubes once a month, ... an easy job. Bias drifts and that is also part of the care and feeding that goes with older ARC amps. That said, I understand that new ARC Ref 140 is self-biasing and has a resettable circuit breaker if a KT-150 arcs. Very nice but very expensive.
I am sure you will make a good and practical decision. I don't know your budget, and that should have been the first question, but if you like ARC tube amps and have the budget, give a thought to the Ref 150SE. It has (I) a very robust power supply (1040 joules), (ii) can easily push out 150 watts into an 8 ohm load off the 8 ohm taps, and (iii) has a relatively low output impedance for a tube amp (approx. 6 ohms off the 8 amp taps and even lower off the 4 ohm taps).
Good luck and stay safe.
BIF