DAC Suggestions for Aurender N100C

Suggestions for DACs that match well with the Aurender N100C (basic N100 with coaxial option).  I have mine matched up with a Schiit Audio Gumby.  The overall sound is good, though there is often a graininess that is an issue.  I exchanged my first Aurender (thanks Music Direct), but the problem persists.  I've used USB and Coaxial.  Now I'm wondering if it is the synergy (or lack there of) with the Gumby.  
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I recommend you audition the Ayre Codex DAC.  Its list price is $1,995.  AND, there are 2 listed for sale on Audiogon.  One Ayre Codex DAC is listed at $1,150 (8/10) and the other is $1,364 (9/10).  The Codex DAC supports USB and Toslink outputs only.  The Ayre Codex DAC is a great sounding DAC.        

I have an Aurender N100 (not the C).  I would expect that the performance of the two units are similar despite mine being USB only.  I have compared the unit directly to the Bluesound Node 2 and Lumin U-1 - in both cases going into a good outboard DAC.  The Aurender bested them both.  The Aurender isn’t grainy to my ears though I expect going further up the food chain on a streamer would show deficiencies.  So, I’m guessing the issue in this case is with your Gumby.  The DAC I use is the one built into my NAD M12 Pre/DAC.  That’s not a good option for you unless you need a new preamp.  I here wonderful things about Schitt’s top end DAC. Is that within your budget?  If not, I’d bet you could find a used Rega DAC -R for a reasonable amount. It’s pretty smooth too.
I agree with hgeifman’s recommendation of the Ayre Codex.  I have used one for the past year with excellent results. Very smooth and revealing. Only replaced by moving up to the Ayre QX5/20. I will be listing my Codex soon.  
@mgrif104 I have compared the Aurender N100 to a Lumin U1 and the Lumin was superior. Perhaps you meant the Lumin U1MINI? If not perhaps you should upgrade your DAC or USB cable.
I have a PS Audio Direcstream DAC.  Excellent DAC and very good discounts can be had for a new one (~40%]
Sfseay - it was the Lumin U1 Mini.  My bad.  In that comparison, the Aurender had clearly superior soundstaging.  The detail and tonal qualities were about the same.  

I’d actually like to audition the U1 as I’ve heard good things about it, but I also found the app to be inferior to Aurender’s conductor (and even the Bluesound OS to be honest). I tried to give it enough time to become acclimated. But, I would expect the full sized U1 to be better than the Aurender - as it should be at $2k more.  

I’m using an Exogal Comet with my Aurender N100H via USB with excellent results.  
Awesome feedback and some good food for thought.  The Ayre wasn't on my radar, but I have been considering the PS Audio Directstream.  I like their topology of utilizes software updates rather than needing replacement because of new chip technology.  Thanks.