I have a pair of Sennheiser's 650 and I don't like them. I bought them for myself on Christmas about 5 years ago and they just don't thrill me. They were a disappointment on Christmas day and haven't improved. The high end just isn't there. I'm using a Rotel preamp RC-1070 to power them. Its it the amplifier, the phones, or my 62 year old ears?