The Prima stuff is very nice but their is a magic in the Triode 25 that is very hard to beat, and the Triode 25 can be purchased with a built in dac, which is a very nice combo.
I have an S6 which is basically the same circuit with an extra pair of output tubes and the midrange is incredible, sound stage is huge and the bass is surprisingly good.
The Triode 25 requires a good match with a pair of speakers if the match is good you will have more magic with the Unison then the Prima.