Hi rvrrat,
The dates that you are referring to are on the circuit boards and have nothing to do with the age/model of the amplifier supplied to you.
As others here have noted, we never sell refurbished or returned Axiom products on the Axiom web site or in the factory outlet store.
Engineering changes are made and introduced as an ongoing process. The addition of the subsonic filter was not meant to substitute for the trim switch. The filter was felt to be a useful addition for fans of vinyl playback, to remove subsonic garbage below 20 Hz caused by turntable rumble, tonearm/cartridge resonances, and other record-warp anomalies.
The trim switch was felt to be of limited utility. I've never used the trim switch on my own EP500; some customers like JohnK, have found it useful.
Regards,
