So I'm using a Raven Labs headphone amp for practice and am looking around for some good headphones to use with it. I'm strongly leading towards the Beyerdynamic DT-770 Pro's. Was just curious about the impedance. The specs on the headphone amp are: 'Headphone Out, 75 Ohms Impedance' The Beyers are available in 80ohm or 250ohm versions. The guy at the shop said most people buy the 250ohm versions so that's all they carry but can order the 80ohm in. Will the 250ohm version be too quiet for the Raven Labs or is that where the headphone amp will actually help? Cheers!