note that this depends on how much gain your source has. My digital source is pretty low output and this gain would definitely not work well with the HD650 in my case, as I felt that 7 (isn't that the next step up that amb lists?) was lacking a bit when listening to swt61 beta22. He listened as well, as I'm sure he'd agree. You can definitely start running into (too) low output source with various CDPs and of course phono stages. Just something to be mindful of.