Recommendations For Upgrade AES/EBU Digital cable up to $500

Try DH Labs AES EBU cable from Upscale Audio if you need a return policy. Or check what’s available in TMR and call them for a recommendation 

I use this one between my grimm and my lampi. Love it. Don’t even think about any digital cable that isn’t at least silver plated.

Price is in $can so it is pretty close to your price range with the strong dollar.

https://audiosensibility.com/blog/products-2/digital-cables-occ-copper-and-occ-silver/#!/Signature-SE-Silver-AES-EBU-XLR-Digital-Cable/p/559064559

From the what you are saying I would think a high end used Cardas... Clear Beyond would fit the bill.

Check hifishark for a used Acoustic Zen MC2 — they do pop up fairly frequently and are easy to re-sell if it doesn’t work out cause they’re always in demand for good reason. I have one and think it could be exactly what you’re looking for and will kick the snot out of any cable that retails for $500. Read the unanimously glowing reviews, and best of luck.

Here is a good source for cables.

also, if you’re drinking the Kool-Aid, they have a great lending library. 
https://www.thecableco.com/cables/digital-cables/digital-aes.html?p=2&product_list_order=price_desc