GeorgeO ,
Cadence ARCA are 91.5 to 92 dB efficiency , so 25 watts power from a tube amp for a 23 x 13 ft room should be adequate, I believe. Presently I use Jamo Concert 8 series 90 dB Monitors . They are handled fine by my 25 watts tube amp and I do not feel short of power. . So I believe ARCA shuould not pose a challenge in same room with the same Amp.
I do like to take your tip to audition ARCA , which I can do with my own Amp . I think , one of these days , I will go to Pune with my Amp to audition ARCA. Only thing is , I will not be able to audition other shortlisted spkrs for comparison . So the decision will have to be on stand alone basis of " I like the sound or I do not like the sound ".