FirstWatt SIT-3 or Pass Labs XA25 for Avalon Indras?

Hi, I have a dilemma, SIT-3 or XA25 for my Avalon Indras that are 87db and 4ohms? 
I use to listen at night at low volume, mainly chamber music and opera, but also orchestra. I like the warmth and three-dimensionality and the reverb of music auditoriums.
The preamp is a Dissanayake custom tube and the speakers are the Avalon Indra, both wonderful.
Of the SIT-3 I read that it drives 4ohm well, that it has a warmer sound and has more soundstage than the XA25, all of which leads me towards this model.
Of the XA25 it struck me that it goes down to 2ohm and is very detailed.
Power is not the key point, if I listen to music during the day the knob never goes beyond half of the current power amp which is a 50W Bartolomeo Aloia Micropal.
The aim is to have magic and involvement at low volume.

Thanks in advance for suggestions!

Alberto