BiAmp Focal Kanta 2 speakers with 1 set of posts.

Since you mentioned running in mono, I think what you’re talking about is running the 2 Evo 400s as mono blocks with one amp driving each speaker throughout the full frequency range…That’s definitely possible and should make some improvements, the value of which would be relative. 
 

Bi-amping a speaker means using a different amp for the tweeter than for the woofer on the same speaker. That setup would require one evo 400 driving the lows and the other driving the high frequencies each still set in stereo and connected to separate binding posts on the speakers… you can’t do that without separate binding posts unless you’re going to do some surgery on those beautiful speakers. I would not suggest this plan. 

Get the other Prima Luna, drive each channel by one and enjoy another or 2 of performance.

Maximize the potential of those speakers by getting them in the optimum position, along with attention to the room.

One of many ways to find the "perfect" spots for your speakers.

http://www.cardas.com/room_setup_calculators.php

Speaker location and room will do more than what you're thinking of doing.

 As mentioned, your speakers are not  setup for separate amps to drive lows/mids and arguably wired in a "better" configuration-single post.

Thanks for this helpful advice and link.

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

@tablejockey i did not know the OP already had a primaluna 400 as that was not stated in the initial post.  I do not like criticizing peoples choices and would have abstained from this thread had I known.  
 

Those amp aren’t my first choice for those speakers.  Given the OP already has one, trying a second one could deliver better results.  If I was the OP, I would see if my dealer would lend me a second amp to try in this configuration.  If it improves the sound in a meaningful way, outstanding!  If not, then he can explore different options if he is unhappy with the single amps performance.