A $400.00 preamp is audiophoolery.
As I said an RIAA eq. circuit is simple.
Here is a classic circuit that can be made from components that are inexpensive, and its a good circuit.
That is for two channels and is what the board would look like.
There is no advantage to adding complexity. So a really good RIAA phono preamp does not need to cost $400.00, although there will be plenty of scoundrels ready to part you from $400.00 and up for this simple device.
The point I really want to make is that if you get roughness known as distortion as you increase volume then the power amp, speakers or both are where you need to look.
As I remember you have pretty robust speakers. However you have had a fairly new receiver fail. Receivers are not high power devices, and generally will fail of you use them as such.