laptop to DAC wireless ... what's the best way?

I'm pretty sure you can do it with an Apple Air Port Express. Works with PC as well as MAC.

Unfortunately, the USB port on the Airport Express does not output sound. It only works with USB printers. The 3.5-mm audio/optical jack is the only way to get sound out of he Airport Express.

You can find AE's for ~$30 used. Depending on what DAC you currently own, it might be less expensive to buy an AE and replace your DAC.

Or check out the "NAD DAC 1 Wireless USB Digital-to-Analogue Converter".

There are a lot of options, but the performance is all over the map:

AirPort Express - toslink out
Squeezebox 2,3, Duet and Touch - no longer in production
Sonos

The easiest to use is probably Sonos, but it sounds really bad without reclocking. Go to sonos.com for a demo. Probably the most popular world-wide.

Steve N.
Empirical Audio