I've never really considered spending much more that $100 on headphones until joining Head-Fi. I started out with Grado SR 60s about 10 years ago when I listened to more rock. Over the last few years I've gotten into a wider variety of genres. I'd been using aweful earbuds at work for a long time since the Grados leaked way too much sound. I finally shelled out a few bucks and got ATH M50s just to leave at work and I think they were well worth the money. I just ordered a pair of NuForce HP-800s since they seemed like a good deal at $50 and I wanted to try something out that offered a bit more bass.
Now I'm thinking that I'm willing to spend about $500 and get some more serious equipment. Maybe some good cans and a decent DAC / AMP combo. Portability is not really a concern for me. I'm looking for something to use at home where it's pretty quiet and I can close the door of my office, kick back, and relax. After doing some reading here it seems like the Sennheiser HD600 / HD650 are well-rounded and popular choices. Also the HiFiMan HE-400 look like another option that are held in high regard in a similar price range. When it comes to DACs and AMPs (or combo devices) I've really got zero experience. I've been doing a bunch of reading here on Head-Fi of reviews and figured it was time to stop lurking and just ask for some opinions.
If you had $500 for a good all-rounder set of of headphones and DAC / AMP what would you get? Do you ever find yourselves going back and listening to your old (cheaper) headphones after upgrading or do they just collect dust?