"But even so, five out of the six you mentioned will all start to press the 'hard zone' of some of the budget monitor controllers we were discussing."
Really? Would you really want to be running an AI that close to its limit? Surely you would want to be 10dB under nearly 1%thd?
It depends whether you're talking about digital or analogue on your audio interface
I run the digital output of my ancient Echo Mia into the digital input of my Lavry DA10, and that can generate extremely high output levels with no 'hard zone'. Set to maximum it can manage 24dBu balanced = 34.72V peak to peak = 12.28V r.m.s