@russ69 What was tuned up? How was that done?
Are these systems super bright? Or what does resolving mean here?
Well, it would take a book to tell the whole story but there are many ways to get where you want to go. The way I do it is find the right loudspeaker, the right amp for that speaker, the right tubes for the amp, the right preamp and tubes, the right source, the right speaker placement, the right room acoustics, and finally the right cables. (Lots of experience to do that, which means lots of wrong choices)
I don't do it, but maybe simple tone controls or frequency correction would be another way. (I'm not a fan of this method).