Digital coax from CD player to DAC, RCA or BNC-RCA?

I've been using my Marantz SA8005 as a DAC feeding a RLD-1 to a recently modified DNA-1. I will be swapping in a Stellar Gain Cell DAC and will try it as a preamp as well. If the synergy isn't there, I have other plans for the SGCD.

That being said, I would like to find a good digital coax and hear that a BNC cable with RCA adapters is a possible option over a cable terminated with RCA.

I've researched some of the topics on graphene but not sure where to start.

Would like to keep this purchase under $400, and I hear 1.5M is where I should be in terms of length at the shortest.

Open to all input and criticism, also feel free to PM me.
I also don’t care for adapters
As a general rule I don’t either — less is more.  But I too was told by someone who designs expensive DACs that it’s preferable to run a balanced digital cable with RCA adapters than one that’s RCA terminated.  I don’t know why and have nothing to back this up, and I’d also think it depends on the quality of the adapters as well so they don’t do more harm than good.  Interested in what others think on this. 

Post removed 
Thanks for all the input.

@dabel I did purchase a Nordost Silver Shadow BNC digital coax with the RCA adapters from a member here, NIB. Thank you for pointing me in that direction.

I will gladly report my findings once everything is up and running.
Post removed 
I did a bunch of testing and made several attempts to test different RCA plugs in a digital cable.  In all instances, the sound was always the best using BNC connectors on the end of the cable and then attaching a BNC-to-RCA adapter.  I tried DH Labs RCA-750, WBT Nexgen and even  Furutech CF-102 (Furutech was the worst).  Using just RCA connectors on the cable resulted in high frequency loss in the audio when compared to BNC cables with BNC-to-RCA adapters.

The highest resolution BNC-to-RCA adapter is the Black Cat adapter, but the RCA plug doesn't have a lot of grip so heavy cables will tend to cause the RCA plug to lean down.  Otherwise, get the cheap gold-plated BNC-to-RCA adapters from monoprice and different distributors.

The Canare BNC-to-RCA adapters are not good and cause the sound to be messy in the high frequencies.