Turntable and cartridge setup known for a marvelous bottom end.

Some of the best MM cartridges from the dolgen age of analog can reproduce bass from 5Hz, I doubt there is anything like that on the record, but if you will look at the specs of the Audio-Technica AT-ML170 or 180 you will see frequency response of those marvelous cartridges: 5Hz - 42k Hz for AT-ML180 and 5Hz - 40kHz for AT-ML170. Those cartridges are spectacular.

Anyway, if you have bass issues you have to studdy room acoustics, it depends on your room size and position of your speakers (and your listening position). Do not change any gear until you will find a sweet spot in your room with your speakers. Various methods published online. 

At 5Hz, any cartridge/tonearm will be at or below its resonant frequency, at which the frequency itself would produce an apparent peak in response.  Furthermore, can one encode a frequency of 5Hz on a record?  I have to wonder how one could measure a true cartridge response at 5Hz.  Seems wishful thinking to me.

I think there is nothing below 20Hz on vinyl record.

But you can feel it?

"Right now, the Pro-Ject Classic goes to a Pro-Ject Tube Box DS2 then to my AVR Dennon 45H for amplification."

Put some USA Baldwin (Raytheon) 1959-1962 yellow label NOS tubes in the DS2 if you want it to sing at its best. I've tried them all and these tubes were by far the best. Can be had for well under $100 a pair.