jonlai9As an amp, this sounds pretty monotone/unimpresive with my DT 880 (I know, a different beast than the 650's, but worth mentioning), compared to my S.E.X. amp. I use this solely as a DAC, paired with a nice NOS tube, and I couldn't be happier, for the price. If you're looking for a worthy partner for your 650 without breaking the bank, I would suggest the Bottlehead Crack, or even the S.E.X., which I love by the way. These are DIY amps, but don't fear the soldering iron. It's easier than you think, worth every effort and makes it that much sweeter to listen to. Happy listening!