Why get a separate DAC

I just put together another system in my house. Hegel h120, LRS speakers and BluOS streamer. I had never been exposed to DACs before because my main system is 20 years old. Question is whether a separate DAC is recommended. Obviously the Hegel has a good DAC as does the streamer. What do folks think and why? Thanks 
I believe DAC technology will continue to improve for years to come. That stated, having a separate DAC makes the most sense to me.

Just my opinion 
Well you have 2 DACs now. What is you want to improve over the sonics of them? Which do you like most? 
I own a Hegel h160, and have found my Denafrips Pontus II DAC to be superior to the internal one in the amp. It also provides more flexibility (e.g. OS/NOS, more digital input options).

This is not to disparage the HEGEL DAC at all, as it does a good job for an all-in-one integrated.

Why get a separate DAC

It’s said, digital cd transports and separate dacs, are at a disadvantage as each have their own clock (and are not syc’d together).
With a combined one box cd player there is one clock and both transport section and dac run off it (and are syc’d together).

There are some very expensive separate transport/dacs EG: DCS, Wadia etc etc that had a separate connection lead that let the transport run off the same clock as the dac, and not it’s own.

Cheers George

The DAC in your Hegel H120 should sound better than the internal DAC in BluOS streamer. You may prefer the BluOS app interface better / versatile compare to Hegel. If you want to keep things simple, use Spotify Connect with Hegel and call it a day.

My advise would be to enjoy Hegel H120 for now, get your feet wet with streaming. Down the road you can step up to better streamer / DAC separates.
... because of better sound coming from a better dac... or at least the prospect of it!
I use excellent power and interconnect cables on my node 2 and I haven't bothered thinking about trying a separate DAC because it sounds so good.

But my cables are extremely good and cost more than the Node 2, 

Regards - Steve