Is low cost DAC worth it?

Sorry to hear you are not getting much of an improvement. Sounds like your system is not resolving enough to make the difference obvious. Hopefully, you can return the stuff.

OP,

I’m an old fart as well. Most of us have hearing that is compromised in some manor. But typically it will not take away the enjoyment of better sound, since better reproduced music sounds better in all frequencies. So, just because you may not be able to hear the highest frequencies (for instance) you can still appreciate the richness in the midrange and low frequencies. Also, having good undistorted high frequencies will impact the lower frequencies in a positive way.
 

Also, listening is an acquired skill. My partner has always had better hearing than I (most women do), but I could always hear all sorts of nuances that she could not. Such is the enjoyment of well reproduced music.

OP,

Pretty soon you are going to hook up a decent streamer and DAC and hear why they are important. However if you don’t invest some money in both it will sound like a waste of money. So far you have been splashing around in the kiddy pool.

OP…”Here is another way to consider my question.  Are low cost DACs (such as the Schiit) going to be any better than the DAC in the Apple Airport Express?…” 

YES.