Streaming from phone

The iPhone supports "bit perfect digital streaming". You need a USBC to USB-B (the one on the DAC).

So, this way the phone acts as the streamer and transmits to the cable directly. 

iPhone → Apple USB-C/Lightning to USB Camera Adapter → High-quality USB cable → External DAC

I’d start here. 

If you want you can use the cell phone to do the wifi and a streamer / DAC to receive. 

Be careful. You may need to use an Apple cable as second party USB cables do not support 24/192.

If you get a Bluesound, I’d recommend. you can try both ways and see which sounds better. 

Any suggestions for good streamer with wifi?

It depends on how hi-fi you want to go, streamers make a difference. You are not limited to streamers that support wifi, you can use a cheapo TP-Link wireless extender to handle those duties. Going up the chain a bit on the streamer would give you better results. All that said, Bluesound is a decent mid-fi choice and has good control software that won't drive you too crazy.

@ghdprentice -- the one catch with your suggestion is that it requires a cable connection between the phone and the DAC.  Not everyone wants a long cable from their listening chair over to the stereo. Hence the several suggestions to use the phone as a hotspot and control for a wifi streamer. 

If you are planning to go iPhone to Bluetooth Receiver (part of amp or separate device connected to the amp), you may want to consider the Questyle QCC Dongle Pro ($77.00 on AMZN cyber Monday). It gives the earlier than 17 iPhones LDAC capability. I found that it really improves the sound to my LDAC capable wireless headphones and earbuds.

@mlsstl 

Good point, the more complex gives you a remote (freeing your phone).