I think you'll hear improvement even with a short run. Some balanced interconnects make more difference than other ones, like MIT or Synergistic Research.
Do you need to use ALL balanced cables?
I have: XA7ES CD Player: w/balanced & unbalanced outputs GFP-750 Preamp: "" SF SFM-160 Amps: unbalanced only (feeding Virgos) I have decided I like the sound of the passive preamp verses the cd player's variable analog outputs. I am currently using unbalanced interconnects between the CD Player and the Preamp. Will I see improvement if I spring for a set of balanced cables to connect the Cd and preamp?