Play music from laptop over WiFi to existing audio system: how?


I want to play music from my laptop to my existing stereo system over WiFi instead of a USB cable. I find plenty of systems designed to stream music from the Internet but I'm not interested in that. I want to play the music from my laptop. I also find plenty of USB DAC's but I don't want to have a USB cable. I also don't favor Bluetooth because WiFi offers my bandwidth and options.
I looked at the Yamaha MusicCast WXC-50 and while I see that it can access files over the network using NFS (my preferred network file share protocol), it appears that in this case the laptop act as be a passive storage device. I am hoping instead to use the music player on my laptop to send music to my DAC/preamp as if it were connected by USB cable. But, of course, I want to do this wirelessly.
Is there a solution similar to what I am looking for?
lowoverdrive
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I have a an Onkyo P-3000R preamp / USB DAC. It is not WiFi capable. But I did not even find any WiFi capable preamps that will do what I want.

I am happy to add another piece of equipment and I would welcome recommendations.
My file formats are FLAC (mostly) and some MP3 (when I cannot get FLAC). My Onkyo handles those and more, as does my laptop. I just need a WiFi connection to replace the USB cable. How?
Any wireless streamer, Bluesound, Auralic,etc will stream the files from your laptop just fine. That would be all you needed whatever streamer you had would be on your wireless network and on your rack and you just run a digital cable to your dac/preamp.
Save money. Use existing smart phones or tablets (don't buy custom streaming devices) and Install plex server on laptop (free). and create a library. Install plex app on a separate phone laptop or tablet (~$5 each). Connect digital out to dac and dac to pre-amp. Or use analog y connector from headphone jack to hifi/preamp input to use dac in phone or tablet. Cast from plex on laptop to device connected to hifi. Play music and enjoy. If you have another phone or tablet install plex app there too and use that as a remote controller to the device running plex that is connected to hifi.

Is Plex server available for Linux?

> Connect digital out to dac and dac to pre-amp. 
Digital out of which device is to be connected to DAC? You are saying don't buy any device, so I don't know which device you are saying will connect to the DAC. Or are you suggesting installing Plex on a dedicated computer (like a NUC) and positioning that near the DAC?