Headphone/Amp Combo for under $800

First, go to headfi, the website. It is all about headphone listening and amps. You will get more feedback there than here due to its specialty based site. That being said, AudiogoN is the best website in the world!

That being said, headphones are very subjective and one person's likes are very different than another person's and many people have limited experience and therefore can only make recommendations based on very restricted listening. Headfi you will find true afficianados and more experienced feedback.

things to consider:
Do you want to take you phones and amp with you when you travel?
What do you have access to listen to locally (stores, other members of this or other sites)?
Open back, closed back, in-ear, etc. . .

I had a couple of pairs of JVC Victors (very nice phones) and sold one pair to a guy who I delivered them to. A real headphone guy. He had 3 headpone amps and about $20K worth of headphones (that's why I delivered them). I got to listen to a lot of different combos and there are huge differences between amps and cans (much more so than with speakers - in general).

Why don't you start out by reporting where you are located, you may be surprised to find other members are open to helping you out (ie. listening to their equipment).

I have Senn HD 600 which are amazing. I went with them over the 650 as most reports were that the two were basically par minus a smidge of bass. I thought about getting a headphone amp, but was quite pleased with the sound from the headphone output on my receiver (a marantz now, and formerly an older Sony ES). They even do ok, but with limited volume, through my iphone or computer.

One word of caution, do not buy from amazon as I tried that and ended up with a defective pair of headphones with a missing serial number. I bought mine from an authorized dealer and paid the extra $30 or $40 over amazon after returning the ones that were defective.

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?