What is the most important cable in your system

YEP. PREAMP TO AMP THEN FOR ME.POWER CORD TO PREAMP

Well, since I have a Bel Canto E1X integrated amp/dac/streamer, it's the power cable of course - Cardas Clear :>)

Perhaps the primary power cable (Shunyata Alpha v2) that connects to my passive mains power block (Shunyata Denali v2) feeding the whole frontend of my kit from the city mains source. The interconnect cables from my preamp to mono block amplifiers might well be the most significant if it were not for the dual differential balanced topology of the Atma-Sphere gear on either end. Which renders the cable basically irrelevant beyond a decent Mogani studio grade XLR. 

The power cable. Without it, nothing works.

@sandthemall 

I agree too, phono cart to phono amp.  Because the signal is so low level it needs all the help it can get transmitting the music truthfully and without external interference or noise.

With a parallel tracking arm I need to use silver litz wire into locking plugs and junction box.  I run my whole system balanced so I can use high quality XLR terminations and from the box to the phono amp.