Tuneslover
Headphoneus Supremus
Without the mod they were unlistenable for my ears. I would've sold them immediately. I've heard cans that I needed to get used to but I still liked them enough to give them that chance. Unmodded the 650 was not something I was remotely interested in. Dark, muddy and veiled, for my own ears. With the mod they are much better, but still very hard to get used to. But I am still listening. Jazz sounded great (but still dark). Classical sounded awful. Pop/electronica sounds pretty good. These seem to work best with bright recordings to balance out the dark signature.
I suggest you plug your 650's into your Jot, connect your Modi MB to your Jot and it to your source (I think you use a CD player, right?) and put it into repeat play for 2-3 days. Then with an unbiased mind begin to listen to the truly terrific system you've assembled.