A lot of phones I tried turned out to be disappointing, with some deal-breaking irritation or just plain lackluster sound so that the phones collected dust and were eventually sold.
The TH900s are the opposite; over time they just got more thrilling and I am more in awe of them than ever.
Just my 2 cents and my subjective experience for those considering them and any owners considering selling or returning them.
I think you should give them time or try to scale them with better upstream gear. They really deliver with care and feeding.
They are phones that have a sound that really touches my heart. I love these phones.
I can even name a few culprits, Your Honor :
HD 800 (main offender)
LCD2 (main accomplice)
Grado GS1000 (would-be second knife)