Headphone/Amp Combo for under $800

If it is neutral you are after then the HD600's will come closer than the HD650's. The latter emphasize bass a bit more and dip in the treble more than the 600's, and all of that is quite audible. I personally found them damned boring cans mayself, but they are certainly on the neutral side. I listen to all of the material you list and would recommend a more lively can. None that I've tried (and I have tried a few) do absolutely everything right, so you may want to set your priorities among the music you do listen to, as well as the qualities you value from a headphone (bass, treble, soundstage, vocals, etc.). Grado's are not neutral cans, but they certainly can be very enjoyable. If you do enjoy a lot of rock, their RS-1 or HF-2 (I think the latter is only available to Head-fi members from TTVJ.com) might be very fun choices...but not neutral. If you stress the vocals, classical, acoustic thing, I might suggest ATH-W5000, which is a rather warm can as I recall, and is also of the few closed cans that do a very nice job at some sacrifice to soundstaging (a bit overrated on headphones IMO). Choose the amp according to the headphones, just as you would for speakers. My .02 Lincolns on the AKG702 - on three different amps they just did not occur to me to give the music the weight that seems more true - they sounded a bit thin, and are very picky about amplification. They are definitely a lighter, airier sound than the Sennheisers recommended here.

Amp would be the Cayin. Once you have that I would suggest trying different heads till you get the best fit to your listening tastes.

Jax, I do not want to collect another Senn cans ( my HD 280 pro/ HD 595/ HD 650 still have not enought burn-in time yet) BUT the HD 380 seems to have a very high rating. What's your take on the HD 380 pro and the ATH-M 50? Are they all-around good for non critical listening or just hypes?

Andrew- I have no experience with either of the cans you mention. I'm a reluctant headphone user (much prefer speakers) and use them only when my wife requires quiet. Over the past ten years in using cans I've probably gone through as many different headphones, so compared to those who've embraced that hobby with more enthusiasm, my experience is limited. Which is why I'm suggesting you check on Head-fi. In spite of the highly elevated noise ratio, there are still a few folks there who come from a solid base of experience (though, alas, they seem fewer and further between than say, five years ago). If your budget were higher I'd point you to two of my favorites: HD800's and LCD-2's (very different from each other, and the HD800 is like no other Senn can), the latter of which I currently own and enjoy, and the former is what I owned before that. The LCD-2 frequency response is desert-flat up to 1K, and then gets shelved down about 10db and extends out to 20K (so a rather unique response). Other than the slightly recessed treble, they occur to me as very neutral cans. If you are way into soundstage and treble, the HD800's might be your cup'O'joe. My complaint about them is the soundstage can almost be a bit disorienting at times, and the treble spike tends to emphasize sibilance more than I'd like. Still, they are outstanding cans. I don't think there is a perfect headphone that does everything perfectly. One sleeper can that you may be able to find on the used market at a decent price, is Sony's MDR-CD3000 (not to be confused with the other 3000 models). I thought that was a very nice pair of headphones that was enjoyable to listen to most material through. I used them with a Berning Micro-ZOTL amp, which paired off really well and is a great amp with the right cans. They seem to be harder to come by these days though, and prices have gone up on them.