Normally I wouldn't reply, having not heard the amps you mention, but I do have Kensington SEs and it will be fairly rare to find experience with those speakers on this forum.
Since you mention the 8b - I've done the vintage amp thing on the Kensingtons. Had a fully restored Eico HF87 and pair of Heathkit W5M. Later got a Rogue Atlas, and just recently upgraded (BIG upgrade) to Rogue Apollo monoblocks (tube, 250 Watts/ch continuous with 1500 Watt transient capabilities). I run the Apollos in triode mode, which cuts them down to about 75% of rated power (still plenty).
I was deceived by the relatively high efficiency of the Kensingtons at 93dB/Watt. Don't get me wrong - I think the spec is accurate. However, when you have a rare speaker like that, capable of achieving high "you are there" volume levels without a trace of harshness or distortion (big conditional on the upstream gear & TT setup, however), then it pays to use an amp that can also push such levels without strain. IME the 50-Watt class amps (and this will include any amp with a quad of EL34s) will compress dynamics and get a bit "murky" at these levels. With high dynamic-range orchestral recordings, you may even run into occasional hard clipping. Even rock recordings (not the biggest dynamic range) will get softened and lose the amazing speed they could be capable of. Rolling EL34 and input/driver tubes was more a change of tone/flavor than anything else. Upgrading to the Apollos was a LARGE, non-subjective improvement in all areas.
If you don't like listening at high levels (to be clear I listen loud, but not at levels that induce ear-fatigue), then a really nice amp of 50 Watts or less could be perfect. However, for me the Apollos have provided the biggest audio revelation I've had in years - well, maybe that's still the Kensingtons since I feel like I've only now REALLY heard them!
I'm sitting probably 9 feet from each speaker, with the speakers about 8 ft apart, in a appropriately sized room for the Kensingtons - so it's not like I'm fighting against huge distances. I feel like I'd severely underestimated the importance of amp quality AND my need for power!
Let me tell you, I'll be spending all my coming nights madly going through records/tapes, since it would be a shame to have not heard all my music like THIS - in case anything happens to me (get hit by a bus, etc ;)).