... Should I be concerned?

Look into the difference between gain control and volume control. In very, very simple terms, volume effects the outgoing signal but does not have any effect on the signal. It simply makes the signal “louder”. Gain control directly changes the amplitude of the incoming signal and has a distinct effect on the signal. The knobs on the back of your amp are gain, not volume. You can do something called “gain staging” where you do exactly what you are thinking and better matching the volume output to the amp gain and overall volume of the system. The trouble is when you “turn down” the gain knobs you are no longer getting the most out of your amp, plus adding potential noise into the incoming signal via the pot. With the knobs all the way to “max” they are effectively out of the signal path and your speakers are getting all the power the amp has. Play with it, see how it sounds. If you like the result, good to go. Otherwise, you may need to seek out a new preamp that is a better output level match for your amp.

huh?

Not knowing the amp specifically i will guess that they are simply a potentiometer (volume control) in-line between the preamp and the input of the amp. yes, they **could** control the gain (the amplification factor) of the amp - but depending on the design this has complications that most designers would avoid due to unknowns in the real world.
So... i'll guess that its nothing more than another variable resistor divider in series with your signal.  You therefore have two - one in the amp and one in the preamp.  You can turn either one, or both, down.  It really doesn't matter. If you turn on all the way up an d"take it out of the signal" as soemone said, you simply must put more of the other volume POT in the signal.  6 to one, half-dozen to the other.  Set it so its most usable and move on.  There are vastly more important things to worry about.
G

Thanks again to all. Be Well -Best Wishes...

@insearchofprat.......Every pro amp I am familiar with ( which is many ), have input level controls, so they can be set, as mentioned above by jnorris, and also, to create level matching, in multi amp / speaker setups. Although a good volume pot might be at it’s best, at max setting, it should be fine at any other level. The Morrison ELAD is a very simply designed unit, and is more of a " straight wire with gain ", as opposed to your tubed preamp. I have not heard an ELAD in years, but I remember being involved in a preamp shootout, comparing it, to much more expensive, well known preamps, both tube and ss, and it showed less character, less sound of it’s own, compared to the others. I would try it, as it costs you nothing, as pointed out by rodman. There is nothing wrong with enjoying tubes, or any active gain stages, in your equipment chain. I like what I like, and I understand, very well, the variety of equipment available, and, the individuality, of every listener. But, when additional gain is not needed, and the stars line up between components ( gain and impedance matched ), for me, nothing like a good passive unit ( I happen to use a top Luminous Audio unit ). It is up to each individual, the sq outcome they are looking for, and without using the ELAD, you can still experiment ( Marantz into the Parasound ), as you will, as well, be using 1 less set of interconnects. Whatever YOU like best, that, is all that matters. Enjoy, stay safe and be well !

Hello,
If these are gain controls instead of volume controls you will need to reset or adjust the gains using a meter. They need to be balanced with one another. They sound like gains due to how sensitive they are. No pun intended. Be careful you don’t mess up your speakers. Please disconnect all components from your amp before adjusting anything using the meter. 

@ insearchofprat - With the Wolze; you can roll 12AU7 tubes and tailor your sound, to your heart’s content.             From what I’ve read about the Morrison; you can enjoy some wonderful transparency.     Two very nice pieces/great potential.     Have fun and happy listening!