Dan's on vacation right now, but I can shed some light.
First of all, uncited quotes are a pet peeve of mine. Without the context of the quote, it's hard to know how to take it. Here is the source of the quote:
http://bottlehead.com/smf/index.php/topic,3997.msg36380.html#msg36380What is particularly of note here is the date, March of 2013. In May of 2013, the Mainline went on presale. Since that time, I do not believe there has been any discussion of a different high-end headphone amplifier. If there has been, it was fleeting, I wasn't in the room, and there hasn't been followup in any of our semi-formal discussions about future products (which frequently include digressions into products that we all kinda know aren't going to happen (and no, I will not provide examples of these)). If you aren't clear on why there wouldn't be further discussions along these lines, I'd recommend listening to a Mainline. The combinations of circuit, technology, and iron of a stock Mainline sounds so much better than most headphone amps it's not even funny. If you are really serious about high quality headphone amplification, the Mainline is a serious amplifier.
The other thing in the thread linked is that PB essentially recommends the Paramount as a headphone amp. Oberst, have you tried this? They definitely sound great on the K1000s. Rig up the cable and try it if you really want 300Bs on your cans.
