Sorry for reviving an old thread, but I too am a big fan of the HD540Ref's. They are my main headphone for around the house. 10 years ago I inherited a pair in absolutely perfect condition, they looked like they were barely ever used. Since then I've used them nearly every evening and to this day the only thing I've had to replace are the cables (big surprise). The headband is held together with wire ties though and it's getting a little rough.
They spend most of their time connected to my computer, where they run directly off the headphone out jack, no extra amp. I prefer a bit of EQ with my setup, about a 1.5db cut around 4k and a slight bass boost below 100hz. But when I connect them to my Yamaha Aventage receiver, they get no EQ and still sound fine, so maybe the EQ is just to correct weakness in the computer's audio.
I've been wondering about something and I've never seen it addressed. How do the 540's sound in comparison to some of the moderately priced modern Senns, like the HD428? Has anyone done any testing along these lines? I've been tempted to pick up a pair of the 428's since they drop into the $30 range every couple of months, but if they don't have sound comparable to my 540's I'd probably be disappointed.
The only other Sennheisers I have are a set of the ear-canal cx870's, and I have to say they sound at least 80% as good as the 540's to my ears. So I'm curious what some of the larger modern Senns sound like in comparison.