a good hifi rig is a chain
sonic 'tuning' can be done in various parts of the chain
the amp is but one part
while i agree that another degree of freedom in sonic tuning in the amp stage is an advantage all else equal, i have always felt the essential (and higher priority) element to get right is have an amp that performs flawlessly in driving one's speakers in a well controlled, neutral fashion.... tuning can be done elsewhere, source, room, cables, etc etc