If the budget is max 15k, i would rule out tubes and go with SS and the choice would be Classe Cam-400 monos. Regarding dwhitt's comment, I doubt vt-100 or similar 100w push/pull valve amp can produce the required synergy with these speakers. If the choice is to go with tubes, at least 200w/ch push/pull is required in order to get benefit. However powerful tube amps are rare and generally more expensive to a similar power ss amp. I also have N800 speakers, Vt-100 is not a match for the load of the speaker. However, vt-200, vm220, ref-210 or a similar power amp which has mimumum 200w with plenty of reserves can perform the task.
To me, with tubes you get a better soundstage, imaging, tonal balance and bloom but you give up a bit of dynamics, transient speed and grip wrt to a ss amp with 800D. It is your call.