This was the curve agreed on by RIAA in 1948 to optimize the signal to noise ratio of playing vinyl records
It boosts the high end in record and does the reverse on playback.
It was well and good as in the days of 78s each company had it won curve, which was chaos.
Here is my vintage 78 rig with the various playback curves.
Here are the codes.
For magnetic tape it remained chaotic, with NAB, CCIR and DIN recording curves. I think there may have been a few others as well.
So the RIAA pre-empted that when Columbia issued their first LPs.
If you want different amps then a receiver/Integrated amp combo is a match made in Hell. If you want different amplification, then you need a power amp connected to the preouts of the receiver.
Just dump the BS you have been fed by lunatics unknown and put together a system that is properly organized and not a cluster you know what.