BiAmp Focal Kanta 2 speakers with 1 set of posts.

For me, I would do the surgery to bi-amp.

The Kanta No 2s are not a perfect match with those Primaluna amps.    The impedance dips a hair below 3 ohms and is a hard to drive speaker below about 120 hz.  Bass will be a bit flabby.  This really is a speaker that is best with warm, SS amplification.  If you really want tubes, something like an LTA ZOTL 40 Reference+ bridged mono or something from Octave will handle low impedances better.  

Full disclosure, I am a Focal dealer.  I have no affiliation with Octave or PrimaLuna and do have a friendly relationship with LTA.  

I already have 1 primaluna 400 amp and  preamp. 

I doubt you'll have a problem using the Primaluna in a bi-amp configuration. I would horizontal bi-amp rather than vertical. I'd buy a more powerful amp for the low-end and use the prima on the high-end. Don't forget a good active crossover. Also use some high-end binding posts if you're going to modify the Kantas.

Don't you just love the dealers who manage to insert a "your amp isn't optimum for the speakers I carry?" 

Tacky Verdant Audio. 

"Perfect match" in audiophoolery.........yeah right