Well, I would have thought someone would have provided some feedback, so I'll put in my 2 cents.
In general, linear power supplies are better suited for high quality audio reproduction. Unless your speakers are over 100 db/w, if it were me, I would get a 24 V linear power supply. The higher the rail voltage, the more power the amp will put out. More power reserve from the supply is always better than less.
Not sure what you are asking here: " How many amps can I go up to with a particular piece of equipment?"
Far and away, speakers is THE single most important aspect of sound reproduction. The amps and source equipment, while important, are often over-hyped. Improving the sound often involves improving the speakers first. The amp just needs to be good match for the speakers you choose.