Which sounds better? Parasound Halo JC1 vs

Parasound Halo JC1 vs Pass Labs X350.5 vs Krell Duo 300 vs Mark Levinson 532H vs McCormack DNA 500 or others?
It depends on the speakers and the listeners personal tastes.
The John Curl designed JC1's will drive anything you can throw at them, even the impossible to drive at their best "Wilson Alexia's". I think they are the best value in big amps.
As you can see below, the watts just keep increasing with lowering impedance, this means they can give great current drive into any load and remain flat in frequency from 20hz to 20khz, instead of acting like a fixed tone control, like some wimpy amps do.

Tested at

They also have one nice feature that let you switch them to much higher 25watts pure class A (they run hot in this mode)which is good when you listen seriously, then you can switch it out for parties or background music, and this will save the power bill.

Cheers George
Hard to say which one sounds better. Owned the Pass Labs 350.5 a great amp but all the amps on your list our excellent must admit have not heard the Krell Duo 300 but I would suspect that all amps are system dependent. Best of Luck