20 feet interconnects

Hi guys, I posted a similar question a while ago. It's time for new power amp(s). I have had my mind set on trying the D-Sonic 600w monos with
a 60.000 ohms input impedance. Now something else came up and these
amps have a low 20.000 ohms input impendance. I need to use
about 20 feet long balanced ICs. My preamp, Coincident Ststement ,has a 500 ohm output impedance according to spec.
Is this bad thinking?
Will I risk loosening highs or lows from this kind of set up?
I'm willing to try a very low capacitance IC like Darwin or something similar.
I've used this set up with a Plinius SA 102 ( about 45000 ohms I p imp )
and it sounded very good to me.
Any input is welcome.
Thanks,
Mikko