Agree, the Kassandra is an excellent DAC and it will fit perfectly with the AC Monos. Not sure if Stavros has ever made a Kassandra with volume control. Is that an option? Anyway the Incito S is a damb god pre-amp, no slouch. The AC sound IMO is near a top TT, full body and dynamics of the scale. If I had the money I would go all AC no question.
Right now I run a passive and seem to get away with it, probably as the Kassandra has an excellent line stage with lots of current (10v) and low output impedance with it. The common complaints or performance traits of a passive of low dynamics, lack of bass and FR changes on volume are not happening in my system. Only thing I did notice a while back was it was bass light at very low volume using my then passive, but since I have upgraded the stepped pot and also added a higher load resistor. Then I ran my speakers as bi-wire. Both those aspects seem to have cured it.
Back to choices, I would try and get to an AC dealer for a demo. It is a big budget / decision here, so IMO you need hands on (ears on) experience. Review and advice on here is great, but the final decision is hearing it yourself. Maybe check these guys out:
http://www.080.fr
Good luck! I am jealous of your predicament.