Class A bias, speaker sensitivity, watts...?

Just music. "Turn turn the volume up slowly until you measure 2.83 V AC at the speaker input" as in the speaker terminals on the speaker? Or should it be at the speaker tap on the amp?

Measuring true RMS voltage with musical signal is generally beyond the ability of a multimeter. That's why @erik_squires was recommending a 60 Hz test tone.

The difference between voltage at the speaker terminal and the speaker tap on the amp is whatever loss is incurred on the speaker cable, which should be small if you are using anything like a normal cable section and length. In any case, considering what you are trying to do, I would measure at the speaker.

@OP Re Boomerbillone's post. It is a little misleading to tie references to distortion to the output devices. Class A operation avoids crossover distortion. However, amplifier distortion is influenced by a whole host of factors so you can still have a Class A amplifier that distorts. There is also the fact that because true Class A amps are inefficient, they may need to be driven harder to achieve high SPLs and thus increasing distortion. That is not to dismiss the benefits of Class A operation - it has a lot going for it when it comes to reproducing music.

Thank you all for the replies and insights. The question was more of a curiosity than anything. I've been into music since the late 60's and audio gear since the mid 70's. Regardless of operation, through a slew of solid state and tube gear, this amp is the best I've had and considering I can't afford to spend big bucks, the system on the whole is very satisfying. 

Shengya is the designer/manufacturer, a home grown Chinese brand that’s been around a while and their amps are quite good for the price. I’ve tinkered with their products in the past.They make other amps on contract for brands like Vincent in other continents that don’t have manufacturing prowess.

Many ’ultra high end’ amps sold to you as European/North American brands are actually designed/manufactured by Chinese engineering. When it gets to European/North American shores, it gets an astronomical markup and a brand name so the buyer can feel like he is in the "ultra high end" club.

Don’t worry too much if you couldn’t spend big bucks.

Thank you all for the replies and insights. The question was more of a curiosity than anything. I’ve been into music since the late 60’s and audio gear since the mid 70’s. Regardless of operation, through a slew of solid state and tube gear, this amp is the best I’ve had and considering I can’t afford to spend big bucks, the system on the whole is very satisfying.

Yes; for.a small office you've got probably 10x the power you need for those listening levels.  A, A/B or other, watts is watts.