Better to buy a high end network player with a DAC?

The obvious advantages of a built-in DAC are simplicity and cost. You are also relying on the manufacturer to provide better synergy between the components, since they have more control and can presumably provide better integration.

However, if you're interested in high-end streamer-only components, consider ...
Lumin U1 (higher model for the U1 Mini)
Aurender N10 and N20
Wolf Audio -- several models
Sonore Signature Rendu Optical SE

Based on my experience with digital, I feel that keeping the components (especially separate power supplies) separate is even more important compared to analog. @antigrunge2 has an awesome thread that talks about this in detail.

@jumia -- the list I provided above was in fact 'streamer-only' solutions. This was in response to your first post -- 

Seems to get a really good player, you need to have it come with a dac.  And these dacs seem really amazing, but you lose independence that a separate dac allows.

As you can see, there are many world class players that do not come with a DAC. I listed a few, I'm sure there are many more.