300B SET Amp driving Wilson Sabrinas

This is another good example of how a mismatched amplifier and speaker "will work" and even sound OK but you are not hearing the speaker sound the way the designer intended.

Looking at the impedance curve (thanks @vonhelmholtz ) the Sabrina is a very difficult speaker to drive. It is a classic example of a speaker that needs a robust amplifier to sound its best. It should be driven by an amp that can double its output with each halving of the impedance - a feat that your 300B amp cannot do. The result of this mismatch is that the speaker will sound weak in the bass. In other words, you are introducing an unintended tone control into your system. Your Modwright isn't specified into 2 ohms but it does provide good power into 4 ohms. However, it doesn't look like it was designed to power a difficult speaker like the Sabrina. BTW, you never see a pair of Wilsons at an audio show being driven by a low wattage tube amp. Most often it's a D'Agostino amp that puts out huge current at low impedances.

Apparently this setup sounds OK to you and the altered frequency response may be a better fit for your room acoustics or perhaps it better conforms with your taste in sound. If possible I would recommend that you try an amp that is rated to 2 ohms (something like a Krell, Pass, or Levinson) and see what it sounds like. Maybe you won't like it but at least you could hear your speakers sound the way the designer voiced them.

It's baffling that in this hobby so few people understand what speaker sensitivity actually means. They just take what's fed to them by reviewers or other opinions and regurgitate it when talking about speakers and how sensitive they are or are not. Someone once said something along the lines of, better to keep your mouth shut and be thought the fool than to open it and confirm the thought. Then again, those that continue to spread the nonsense, think they're right. 

@roadcykler 

What, specifically are you referencing.  Please provide us with guidance.

@audioaholic1 

I’m not saying it won’t work. But with speakers under 90 db efficiency, you will be limited on sheer volume and dynamics. If you have a small to medium sized room and listen at moderate levels, it could “work”. But ideal? No.

@carlsbad2  @jasonbourne71 is exactly right. Live music is extremely dynamic. Have you ever been 15 feet from a drum set?  85 dB is for apartment dwellers. Real men listen at 95dB and piss off their wives.  Sabrinas will do this easily, but that amp will choke.  @8th-note 1++ Even with Klipschhorns that amp is not enough. We use to bottom out Stereo 70's on K horns. Marantz Model 9s did the trick. Sounding OK and performing realistically are two separate issues. I do not want "sounding OK" I want the band in my media room. I want to close my eyes and FEEL like I am at a live performance. I is that feeling that makes people want to jump up and dance. "Working" is not good enough. People are entitled to have whatever goal they like with their systems. If listening to a table radio is their goal then a SET amp is perfect and so simple they could easily build one themselves. @ozzy62 is on the path to success. 

@roadcykler ​

@vonhelmholtz has a valid point. Speaker sensitivity is the volume a speaker reaches with a given power at 1 meter. Have you ever seen people listen to their system at 1 meter from the speakers? Volume drops off rapidly with distance especially with point source speakers. This is why larger rooms require bigger more powerful systems. SET amps are for closets and headphones