I went through a similar conundrum and just got a second Benchmark. $600 on the used market. If you go to the Benchmark website and look up headphone amps they just talk about the one in the DAC-1; they don't even sell them separately any more. Think of it as a high-end headphone amp with a killer D/A thrown in as a bonus. It makes my HD-600's sing and always has enough juice. It matches my studio D/A (which I never have to dismantle now) and I'll never have to wonder about that part of the chain being weak. $600 seems a little expensive for a location headphone amp but it's well worth it.