I'm thinking about moving my SEX amp across the room from the main stereo set-up, so that it's within reach when in the comfy listening chair, to be used exclusively as a headphone amp. I would keep the Stereomour as an input selector, and run one RCA cable pair from the special RCA out I added to the Stereomour to the SEX. My question is: what's the limit on how long those RCA cables can be? If they stretch the whole length of the room, going under the floor even, they might get close to 20'. Will that be a problem?