difference from higher input impedence on amp?

My preamp output impedence is 300 ohms (AR LS-15) or 1K (Aesthetix Janus). In either case, the default 60K input impedence on my Baron amp is way more than 10x, so it should be acceptable. Some comments on these forums imply that a higher delta is better. The Baron's input impedence is adjustable to either 60K or 110k (with effort, via an internal resistor). What sonic or operational change could be anticipated from raising the input impedence of the amp? Worth the bother to experiment?