which $1k used floorstanders for 35wpc tubes?

((I think I'm really sensitive to cabinet resonance )))
The Vandersteen 1CI feature a sophisticated box less approach.
Their low diffraction multi enclosure driver mounting system should work for you, add to that phase and time aligned drivers and are an easy drive with low to Med power tube amps.
I use Quicksilver 25 WPC Mono Blocks with superb results Johnny Cash's voice sounds genuine,like it should, Beethoven flows with dimensionality,and takes string tone where box speakers don't go.
The speaker is well respected and owned by many top electronic manufactures.
I would read the 1CIs owners manual just to get an idea
of what their about.
JohnnyR
Vandersteen dealer.
http://www.tonepublications.com/review/vandersteen-1ci-loudspeakers/
http://vandersteen.com//media/files/Manuals/1cmanual.pdf

Omega loudspeakers

Monitor Audio Silver Series. RX6's can be had for well under a thousand used. RX8's might suit your room and music tastes better.

It would be less of a gamble if you actually told us the name and model of your "35 wpc tube amp".

Also, since your amp and speakers are so mismatched, how do you know that you really love your amp? The NHTs are not bringing out the best of your amp and your amp is not truly showing what the NHTs do best.

I think I'm really sensitive to cabinet resonance (I returned a pair of Klipsches for this reason)

Guys,Try the Box test to hear the cow Moo artifacts
at 20 seconds in as CI sings the words 515 is just a train on your speakers this is what he is talking about.

http://www.songlyrics.com/chris-isaak/515-lyrics/
Cheers JohnnyR