Comparison of latest DAC chips

I own a Bluesound Node 2i which greatly improved sound after I added the Cat 6 cable.  I do not own a separate DAC but am told it would be the next step improvement.  I have done enough reading that it appears the two latest chips are the Sabre or ESS ES9038PRO and the AK4499.  The brands I have looked at are Sabaj d5($469) and a Topping D90($699).  I saw a great review on Audiocircle of the Sabaj D5 which is now a year old.  The Topping D90 is newer and I hear the build quality of the Topping as well as customer service are both better.   Other brands cost more and most don't use these new chips. 

Is there a difference in how these chips sound?  I would appreciate any comments. 
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The Sabaj is now out of stock at Amazon so I am wondering what is going on there.  Topping seems to be more of an established brand.  The D90 looks very nice after watching youtube and reading threads.  I read the article George sent me and it is easier to understand the terms.  Thanks again to all.. 
The Ayre Codex has one of the most delightful output stages, especially for headphones.


+1 on the Schiit Modi 3. It's a hundred bucks! A great DAC to start with.
It looks like the demand or supply issues are causing shortages in items made in China.  Many brands are out of stock.  Sabaj, Topping, SMSL.

Did you try apos audio?