I can only speak for the Esoteric -- you'll find others have their suggestions, but the older Shunyata King Cobra (Ver 1); which I had was UNBELIEVEABLE!!! Check out the Shunyata website and go for their best digital cord, that you can afford (or used) -- you will NOT regret it.
For your preamp -- again, a good cord is critical, but need not be at the level of the player.
I'm running stock cords on my McIntosh tube amps -- but, that's only because the MC-275A does just as well with the stock cord as it would with a mega cord (IMO).