Primaluna amps have very high output impedance which acts as a graphic equaliser into typical speaker loads. Having owned and used Epos ES14's extensively with valve amps in th epast (once owning Tube Technology Genesis mono amps which thrashed mercilessly a quad of EL34's to 100W each for under a year before the output valves wore out [should have bought EAR 509's which were the same price then and new small car money now] and also fully rebuilt and gloriously charming Quad II's into these speakers), I think the ES14 is ok in terms of response alterations with valve gear.
Seriously though, all that hum, noise and added colouration, especially in the bass, but I suppose we all have to go through it at some point... For low power, the Quad VA1 was huge fun if not driven too hard
- and it may well hold some value too...
I still have custody of the Quad II's, but they're ornaments really and only come out to play very occasionally, just to make sure they still work...