hi..i have one and bought it new in pa. at soundex in th late 90's....still have it... and still own 2 other thresholds, s500 optical bias and a stasis 3...had several others including a forte 6 200wpc...sounded awful...just lots of power. both my thresholds were updated by jon sonderberg, but i let the 55 alone. why? because it actually sounds killer to this day....maybe the most holographic sweetest sounding of all the threshold brand stuff i ever owned. even powered my b&w 803d2's really well. has endless bottom end even on those hard to drive speakers...it's imaging is uncanny and the sweetest highs...i do not need it anymore but played it every day for 15 years without a hitch or rebuild. i do not know how they made that model sound so darn good, but it was bargain and still kills other amps i tried back then for 2, 3, even 4 times the cost. an amazing little amp. i used to call it " THE PRIMER BLACK 55 CHEVY WITH NO HUBCAPS THAT JUST BEATS EVERYTHING DOWN THE TRACK" when i thought i could find better sound, but i just gave up back then.....only between 100-200 ever made i am told