I have a quick question, I am on the fence beween the UHA-6S MKII and the Matrix Mini-Portable. I use HD650s and the thing that is holding me back is bass. The matrix review on Headphonia says that the bass is deep and powerful. But my google skills are failing me and I can't seem to find a review pairing the UHA with HD650s.
My dilemma is that I would rather support a US company (nothing against other countries but our economy needs help) but I really don't want to take the chance of buying a portable amp that is top heavy.
UHA-6S.MKII with 209 is quite clean and neutral. I personally hate sibilance and spiky treble and I haven't noticed any exaggerated treble. From my understanding the 8610s have slightly less treble than the 209, so that might be an even better way to go for you. FYI while I don't have HD650s, I did try it with all my current cans and also LCD-2s, which should be a good indicator of how it'd behave with the HD650s.
Edited by Defiant00 - 2/24/13 at 4:00pm