No problems with the VSA driving the Tonian or the 8ohm KCS
I used sophia princess mesh plates in the amps and did not try anything else.
If you read Roy Gregory's review of the amps in HiFi+ you will have my opinion as well. He is spot on in his description of the amps and it's performance relative to other tube and amp topologies.
I have also owned and used both the TEAD Linear A and B amps and also the tube distinction stereo 30 soul amp (and many others). I prefer the VSA to any of these but all are very good amps IMHO .... provided they are paired sensibly with speakers.
I used/tried a variety of preamps...I mostly used the Tube Distinctions Soul Mate but also tried, Allnic 4000, Shindo (the $18k one), several passives. The amps really let you hear what is going on in front.
I would also imagine that VSA's own acclaimed preamp would be excellent but I never tried this.