Is low cost DAC worth it?

Denafrips Aries II: first choice

Schiit Bifrost 2: second choice

Nothing less.

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.

The 2 DAC’s mentioned by @pmm are an excellent idea. I purchased an early edition Schiit Uber Analog DAC as my first. I used a stripped down laptop with an external power supply and a Cardas Clear usb cable. I upgraded to a Schiit Yiggy, and later added a Project Stream Box Ultra II and ditched the laptop. I also have a Cambridge DAC Magic 200. I gifted my son the latest generation Blue Sound  Node to replace the Bifrost I had given him when I upgraded. He runs a simple system of a vintage Marantz receiver and Klipsh KG speakers. Switching from blue tooth to an entry level streamer like the Blue Sound was an huge improvement for him. Also consider switching to a source that’s not blue tooth. If you don’t want to get an additional streamer, get the Node or something from IfI. Having your system hardwired to the router and the cable that feeds the DAC have a significant influence too. Happy hunting, Mike B. 

A minimum of $750 and up keep in mind a $800dac has under $200 in total 

including the box that’s roughly the average , audio cables much more so still.

Can’t go far wrong with the musical fidelity v90 dac. Stereophile high class B, low class A component. I’ve had mine for Years and I love it.