Actual difference between Apogee AD16x and AD16

Can't get a straight answer. Some say totally different analog circuitry, PSU and clock, others say just better PSU and clock on the "X" version.

Does anyone know definitively? I'll be using an external clock (BLA MicroClock III XB) so Big Ben is no help, and I highly doubt the non X PSU would be so bad as to create an audible difference....but if the analog circuitry is in fact better in the X, that's a factor. $ is tight, trying to save a few bucks if possible on AD and DA. Thanks fellas!

X version has the big ben clock and upgraded converters according to apogee. I never made test measurements of either unit, just installed them as requested.

I have a bunch of AD / DA 16 which I like a lot - soundwise. The obstacles I encounter here are that the DA16 output stages tend to go rogue and start to put out huge DC offsets (several volts) and that one of my two DA16s doesn't remember the wordclock setting after it's powered down. On both issues Apogee was not helpful at all apart from providing their local service contact. I have issued at least two online service tickets for the wordclock issue and it seems that I can't even make them understand what I mean. So I wouldn't expect any aftermarket support from them.

Michael