Full Range Drivers and SET's, why is a classic combo?

I own three SE tube amps: a 2A3, a 45 and a 6BG6. The best speakers in my collection for them are the venerable. Klipsch Heresy Mk1's (99 db sensitivity).

Thanks for the detailed explanations.

rober,

Any experience with  the current Heresy IIIs and SE tube amps? Are these different from the originals  (Mk1s?) in regards to ability to run well off SE tube amps?

Thanks.

If they are still available, the First Watt SIT-3 does a wonderful job with a horn and at 18 watts can easily drive most any horn.  Very tube like sound and a great price

Another possibility for better bass response with still a "SET" sound is a 6W6 Push-Pull Amp that has the screen voltage properly tuned--this will give amazing response.  The 6W6 is one of the most linear tubes made and very beautiful in this configuration with full range driver.  I have come to use this as my goto system--6W6 12W P-P driving a variety of full range speakers in both horn and bass reflex cabs.  Custom transformers from ElectroPrint.  The only SET I really preferred over this was a 71A design, and although the sound was to die for it was limited to about 800mW in a single tube configuration.  As you move up the SET family (71A, 45, 2A3, 300B, 211) the sound gets progressively less clean and a little of the sound stage disappears at each level IMHO.  Not that the entire family isn't amazing--just that the lower the power, the better the sound, again IMHO.