Need some treble

Seems to me that, if you're not hearing high frequencies, boosting them via tone controls may do nothing.

Much like having a null in your listening room. 

My question would be. Do those cymbals reappear when you crank it up a few notches?

Go to Costco (etc) get hearing aids

My high frequencies are attenuated, not non-existent, so boosting them makes sense to me.  Getting ready to order my Lokius.

Sounds like the equalizer is your best bet. It is hard to imagine that putting hearing aides in the loop would result in better sound across the spectrum. 
 

Tell us how this works out for you.

Good advice in above but be careful with EQs and boosting treble. It can burn out tweeters.

Maybe try some super tweeter ad ons. Your pets may not like it, but they can just 

leave the room.