The main benefit of adjusting gain at the pre-amp it to match the amp(input sensitivity) and speaker SPL. Too much gain and/or too much amp sensitivity and/or speaker SPL and you will raise the noise floor substantially and reduce the range of the volume attenuation control on the pre-amp, i.e. the usable level of the volume control is between 8 and 9 o'clock if the gain is too high or the amp/speaker is too efficient. You loose small gradations of volume level which is usually available when your volume control is about 12 o'clock (+/-) on many but not all attenuators.
It doesn't make any difference whether is ss or tube, but the noise floor issue is much more common with tubed units and very efficient speakers (90 DB+) With speakers over 100db it can be critical.
It doesn't make any difference whether is ss or tube, but the noise floor issue is much more common with tubed units and very efficient speakers (90 DB+) With speakers over 100db it can be critical.