Melos MA220 tube phono stage

Some bogus company took over Melos after George Melos. It was located in Las Vegas, not inappropriately. They hornswaggled several Melos owners on incompetent and overpriced repairs, etc. I don't know whether they still control the brand name, but beware of them. One of my friends sent them an amplifier that was first returned broken, then sent back to them, then not returned to him at all, ever. Albeit, this was at least 10 years ago.

I have never seen a Melos preamp. I am not sure what you've got. Is it a phono-only stage or a full-function preamp, which would have a built in linestage section? The way to know that is to look at the rear of the unit. Do you see multiple pairs of inputs, labeled variously "CD", "Tuner", "Tape", etc? If so, it's a full-function preamplifier with a built-in phono stage. And if that's the case, it makes no sense to run its output through your "preamplifier", which is probably a line stage. One reason you may feel it's "pretty good" and not very good is that you are using it as a phono stage. You will remove a layer of distortion if you connect it directly to your amplifier, assuming you do verify it is a full-function preamp.

The load resistances, varying from 47K to 1 ohm, by your own description represent the load seen by the phono cartridge as it "looks back" into the phono input. For high output cartridges, meaning most moving magnet (MM) and moving iron (MI) cartridges, and for high output moving coils (HOMC), set the load to 47K, and forget it. That probably includes the Eroica. The fact that the unit has the capacity to vary the load down to 1 ohm suggests to me that it may in fact have enough gain for a low output moving coil cartridge, most of which sound best with a load resistance of anywhere from 1000 ohms down to 50 ohms. There is no cartridge ever made that would work well into a 1 ohm load, so I don't understand that bit.