I have recently had a listening session with Th610 and Th900mk2, as a sennheiser guy (650s) i really enjoyed absolutely different signature of fostex, though for me both sounded good and the addition of removable cable with same pins as my 650's - it's amazing. Absolutely fell in love with them )))
PS impressions, they're bassy, but not that much, they're warm, but its all under control of your rig (DAC/AMP). They are somewhere below 100 Ohms , so they're easy to drive.
And for me they seemed super comfy, cosy, like something that you have known for a very long time and missed.
What did you like about both of them? And what we're the differences between the 2 cans if you don't mind. ?