If you have the S.E.X. amp with the impedance switch boards you have the option of wiring the speakers connectors in a balanced configuration. On my build i added a 4pin XLR connector and terminated the speakers connections to it so i have both XLR and regular TRS headphone sockets on the amp. Balanced mode does sound different to me, and i do prefer it balanced, it just sounds more precise.
^ I suspect that may be what olegausany is hearing as normally there is no difference between the headphone and speaker posts.