Question about Tone Controls + Equalizers

Schiit has a 15 day return period (with a restocking fee).  You could just order one and try it.  Consider the return shipping and restocking fee a rental fee if you don't like it.

Having said that, in general I don't care for tone controls.  For home theater, EQ is great.  For two channel music, I prefer leaving things flat.  I really only have one device with tone controls, my Vincent SV 237.  They are pretty good and were fun to play with when I first got it, but I have them defeated.

For LP playback, another option to consider is the Parks Puffin.  It allows you to adjust bass, treble, balance, "air",  and "tilt".  I like it a lot, however I ended up leaving everything flat on it after a while also.

Jay73
If you don't have an old fashioned tape loop (to switch it in/out) I wouldn't bother with a Loki. You might find that affordable cables cause too much SQ insertion loss. I have and love my Loki but I rarely use it except for old old fashioned Fletcher Munson loudness compensation for low level background music. 
Most players like BluSound have tone controls or "Soundcraftsman"
 type EQ (foobar, Volumio)
"Alexa play WGBO" (on a hardwired JBL Charge 3) is good enough for background levels for me.
My response to your question is DO NOT use tone to "fine tune" sound.  Upgrade the offending hardware and room treatment for that.

@noromance ...........................

My 7K McIntosh tube preamp has tone controls.  Hardly cheap or mid-fi. Lots of new equipment has tone controls.  If I need to use them, I do.  A dB or so of bass or treble can make an unlistenable cd listenable again.  You never realize how much you miss tone controls until you have them again. 

It seems most here use tone controls to correct deficiencies in specific recordings which is great. There is also the realization that a lot of trouble occurs at the 3-4 kHz region and a slider here would be very useful. Cutting here just 3 db can make a huge difference on records with sharp violins, female voices and such. Also because our ear's frequency response changes with volume (Fletcher-Munson) we become way more sensitive to high frequencies. This is what limits the volume on many systems. On some recordings at volume (95-100 db) I have the treble rolled off up to 12 db at 20 kHz. You might notice that some older rock recordings sound a bit dull. If you turn them up loud they sound just fine.
This is because the mastering was done at high volume and everyone was probably stoned. 
Not to worry Jay. This technology will drift down to lower priced equipment. Just keep an eye on companies like Anthem and NAD. 
Just to see what your system is doing on the computer is hugely informative. Comparing one side to the other there are significant differences between channels. These can be corrected improving your system's imaging. All this is done at very high resolution. In my system it is 48/192. The bit depth is need to cover a wide range of volumes particularly in the bass where you can have 10 db oscillations. Bass you can not deal with entirely with digital correction you also have to improve room acoustics as much as you can. 
It is also interesting that a perfectly flat curve does not sound right. My baseline curve is boosted 3 db at 18 Hz and rolled off 6 db at 20 kHz. You could probably approximate this with analog tone controls.