'Lurk' is hardly the term!
For a speaker like this, a zero-feedback amplifier will need a little help. Fortunately there are two things going for you- the first is that the speaker is an ESL and the second is that there is a way to deal with the impedance.
The ZERO is the way to deal with the impedance and will allow any zero-feedback amplifier to operate the speaker so long as the amp is able to make enough power into a benign load.
The fact that the speaker is an ESL means that the speaker is expecting the amp to make constant power regardless of the load impedance of the speaker (which is why transistors for the most part tend to sound bright on ESLs). The ZERO will present the amplifier with the benign load that we are looking for, and a zero-feedback amplifier will have the proper 'constant power' characteristic.
Class A is important here as a zero-feedback amplifier does not have feedback to reduce distortion. Distortion is reduced by other means- class A is certainly one of those ways as it is the lowest distortion class of operation known to man. Feedback oddly enough causes some types of audibly undesirable distortions and so you are seeing a good number of manufacturers, tube and solid state, that eschew the technique. To do so means that component quality and topology suddenly got a lot more important to the overall success of the amplifier!
So the answer to the thread is: both are almost equally important.
For a speaker like this, a zero-feedback amplifier will need a little help. Fortunately there are two things going for you- the first is that the speaker is an ESL and the second is that there is a way to deal with the impedance.
The ZERO is the way to deal with the impedance and will allow any zero-feedback amplifier to operate the speaker so long as the amp is able to make enough power into a benign load.
The fact that the speaker is an ESL means that the speaker is expecting the amp to make constant power regardless of the load impedance of the speaker (which is why transistors for the most part tend to sound bright on ESLs). The ZERO will present the amplifier with the benign load that we are looking for, and a zero-feedback amplifier will have the proper 'constant power' characteristic.
Class A is important here as a zero-feedback amplifier does not have feedback to reduce distortion. Distortion is reduced by other means- class A is certainly one of those ways as it is the lowest distortion class of operation known to man. Feedback oddly enough causes some types of audibly undesirable distortions and so you are seeing a good number of manufacturers, tube and solid state, that eschew the technique. To do so means that component quality and topology suddenly got a lot more important to the overall success of the amplifier!
So the answer to the thread is: both are almost equally important.