Pass Labs X1 or Krell Phantom II

I had Krell FPB 600c and KPS 25sc and updated to Krell FPB 700cx, KCT and KPS 28c. For sure cast connection makes most audible difference between pre and power. Cd, much less so. So cast is given for a Krell amp combo.

What makes CAST more advantage than XLR?
Clarity, transparency, 3d holographic or bass?
Since you are using KCT, and someone offer me a pre-owned KCT, need your advice and thanks in advance.

I sold all my expensive hifi in 2005 and then i had a a few years with very budget friendly units. But as i recall, cast was better all through. I had a few cast cables and transparents versions was the best. I can only say, from what i heard, i would say this, go cast and don't overthink that choice. You will only end up trying to find a cable (if you go xlr) that will be close to cast. Those amps, FPB 700cx and KCT was really great. I had a speaker manufacturer in my home delivering a set of speakers. He had top of the line Electrocompanet. Among the first thing he told me was, Krell was way better. I think you will find cast cables holds it's value when you go for a Krell amp combo. 

I would  go with Pass as its a better sounding unit.Good luck.

@ebm 
Thanks for your advice.

@sfstereo & rird
Normal dac -> xlr -> KCT -> cast -> FPB-400cx.

Would these setup ruined the sound quality, or I have to get a Krell dac/processor with CAST too?