Is there a way to add "loudness" to a Peachtree Nova 150?

OP, I was WRONG.

I just figured out your Denon Loudness Control. I messed with my Yamaha CR-1040, discovered it’s identical setup. It’s a very good implementation. IF USED CORRECTLY

They both have two volume controls. Standard ’Volume’, and ’Loudness’ (reduces volume only)

FLAT is indeed Zero Loudness, Zero Boost.

’Loudness’ turns only counter-clockwise, in 10 progressive steps, starts at the top, turns left, down, around, back up, almost back to the top.

Each step both lowers the volume a little, and engages ’loudness’ a little, little lower/little more ...

you progressively lower volume with progressively more boost until fully counter-clockwise,(position just to the right of flat is max loudness) it is +10db at 50hz and +5db at 10khz.

1. set ’loudness’ FLAT

2. set your normal volume control for ’low normal’, no loudness.

3. use standard volume UP for more volume

4. for lower volumes with loudness:

a. first: get standard volume ’back to’ normal low volume

b. next: use ’loudness, to lower the volume from there, thus progressively engaging fletcher munson compensation as you simultaneously reduce volume.

c. clockwise back to ’flat’, for ’low normal’. then use standard volume to play louder than that.

So, what's the better option?  Schiit Loki or Chase Tech remote line controller?

I would go for Chase (reminder, needs the remote).

Loki might be a better tone control (4 bands) than the Chase, it is smaller than the Chase

but the Chase is much more versatile as a remote system controller.

remote power, remote volume, remote balance from your seated position is awesome for the tracks that benefit a LOT from a SMALL balance tweak, remote tone, mute, and automatically engaged fletcher munson 'loudness'. 

use it in a variety of ways

I have a loudness control on my RME-ADI-2 dac.

How bout this one? 
 

 Black Ice by Jolida - Foz SS-X Sound Stage Expander