I am listening to my new Senn HD 598SE's, bought for $95. They are playing directly from my MacBook Pro. I am playing CDs I have uploaded into memory with Apple's external drive. To me, these sound very nice at medium volume--balanced, detailed, but need to use the EQ to boost frequencies and volume, then really gorgeous. At 50 ohm impedance, which Schiit amp will work best? I see the Valhalla 2 does best with 300 ohm and higher sets. What is good in that price range? Thanks!