I tried the K2 not so long ago, paired with my Marantz CD63 KI Sig and linked to the Spendors. I concluded that, although it sounded good, it brought no significant gain in performance over the PM66SE KI Sig it was potentially going to replace.
In all honesty, having now purchased and listened to the Primare CD31 and I30, the gains I have over the Marantz pairing are not huge. Yes, the sound has improved, but quite how much I would have to spend to get that major leap is a good question.
Therefore, I would say drop the K2 from the running - I don't expect you would gain any appreciable benefit from it. Pity I never got to hear the Caspian for a comparison.