Influence of DC offset on bias

Are you sure that you can play around with bias adjustment in SS amp?
In most of the SS cases I would strongly recommend not to adjust.

Hifihvn,
In transistors it's the same story only make plate equivalent to collector(assuming connection with common emitter). There's a purpose to adjust the offset so the output is measured the same across collector and ground on both opposite junction transistors pnp,npn pair (I assume that it's a class B amplifier, but I might be wrong) and another channel accordingly. So the offset might be different in transistors (they're way harder to match than tubes and have larger parameter tolerance) but bias current will be the same and 'sound' the same.
Can you tell what kind of amplifier we're talking about?
Brand? Class of operation? Must be a very vintage one. Most of the current ones would have an auto-bias which is a piece of cake to implement.

An auto-bias bases is simply using a reverse conductivity of diode. Depending on how large your bias current should be you choose the diode with the same reverse conductivity current. It's all in the parameter list. There are certainly more sophisticated and advanced auto-bias supplies that allow to match upto 10% of parameter tolerance.

Speaker sensitivity can only tag volume level difference of channels when you listen realy quiet. There also factors to mention such as stereo volume pot. Other than that it has nothing to do with speaker sensitivity.

A SS amp without autobias circuitry or stabilization of quiescent current faces these following problems also previously mentioned by Kirkus:
1. due to the age the parameter mismatch percentage increases.
2. due to the temperature and other room conditions mismatch increases unlike vacume tubes.

There are quite large number of quiescent current stabilization circuits designed and created so far and they have advantage or disadvantage of one to another, but the best ones IMHO is implemented in Bryston amplifiers.

Up until before this post I believed that every SS amp post mid-70's will have it as a matter of fact and quite frankly, I'm shocked of what so-called 'purists' are able to build these days. If you somehow will be able to shoot me the circuit diagram, I'd like to take a peek on that.

As to Meridian 559, I'm surprised. It should be something else on the signal path such as loose wire(interconnect?), solder joint, preamp volume pot etc...

and finally the 105's but only because they begin rolling off right at 20hz.

Are you realy fenomenal or you've just measured SPL to make such conclusion?

I still don't get which amp you've been trying to adjust bias? I've looked at the schematics of Superamp and it has a quiescent current stabilization(an auto-bias), but the offset is being set by Q23 in diode connection and R27 I assume at the factory only once and than sealed.