Is low cost DAC worth it?

I have a Bluesound NODE streamer and a Denafrips Are II DAC.

Given your budget, I would suggest that a used NODE (which has a built-in DAC) would give you the most bang for the buck.  Especially if your hearing or system isn't top-notch, you'll find the NODE's DAC quite satisfactory, and you can continue to stream via wi-fi--the NODE is really designed to work well that way, and it does when you give it a strong wi-fi signal.  The smartphone app for the NODE can also tell you the wi-fi signal strength it is receiving, so you can know whether it is strong enough to stream high-resolution files or just CD-quality files.  And I can hear that hi-res files sound better than CD on the NODE, even using its DAC.

$500 DAC - nope.  Better off spending $500 and upgrading your CDP instead.

A good budget DAC should be a step up from the one in the Airport Express.  Topping, SMSL, and Schiit all have well measuring and nice sounding DACs in you budget.

Another vote for Schiit stuff. Apparently some of you have reading difficulties (or maybe English isn't your primary language) because he was clear about his budget. SSDD. 

Totally Happy with my Topping E30.  It’s a budget DAC and works quite well, quobuz off a spare IPhone XS and running a lighting to USB cable.  I’m getting up to 24bit 192k.