Headphones

The best thing you can do is to audition as much stuff as possible.

The HD600 is really nice but I prefer the Grado RS-1. I don't like way the HD600 smoothes over all recordings good or bad. When the album has bite, I don't want a filtered out kind of distant rendition. You can get a very comfortable fit by bending the headband and tossing the earpads in the washing machine with some hair conditioner.

As for headphone amps, they range from $99 to $5000. Poor to astounding. I didn't really find anything to my liking until I broke the $700 barrier. Lower priced tube amps were seriously flawed in one way or the other.

I have lower priced Grados and old Stax lamba's at home, so I can't help you there

If you are interested in headphone amps and have an interest in a great fully functioning tube preamp, try out the SOnic Frontiers Line 3, (or 2 or 1) it has the Headroom circuitry headphone amp stage and is one of the most neutral preamps on the planet. Great detail and neutrality in a fully functioning preamp. Check out the reviews on their website, the Soundsatge review included the Sennheiser interfacing with this headphone amp.

Headphones are a very personal decision as not only sound quality but comfort is involved.
You can spend hours reading posts here and at headphone websites debating about whether Sennheiser or Grado is "better" and will probably find no conclusive proof either way.
They are both good.
I have tried Senn. 580's at home and have listened to the 600's in various dealers.
However, my personal preference is for the Grado RS-2's.
I do not like headphone amps. I have tried 3 different models, tube, solid state and hybrid and none were much better than the headphone output of an NAD receiver. I should qualify this by adding that the NAD sounds better than the headphone outputs on any cd player or tape deck that I have tried. I have gotten more bang for the buck by upgrading headphones and my cd front end than from a headphone amp.

Although I had initially liked my old Staxes a lot, I sold them last year for $200 as I found I hadn't listened to them for years.
A recording engineer suggested that their uptilted response was great for hyperdetailed recording mixes, but way too fatiguing for extended listening. And so it seemed....
I recently purchased HD600s from a reseller in Germany for $225 (eBay), and find them MUCH more forgiving than the old Staxes. I drive them directly off my Pass Aleph P with a short $4 RCA to phone Y adaptor from the Shack. Sounds great, and they're super-comfy as well.
I'd like a few more feet of reach. Anybody out there know of a clean phone extension cord? I think Senn sells an additional 12 footer, but with a built-in volume slider, which of course won't do! Thanks. Ernie

If you need an extension Headroom.com has best selection. The DiMarzio silver at @$60 for 10ft extension
is very nice, I own one. Really you should look into getting
Clou Blue Jaspis to replace stock Senn cord, it is 3 meters
and looks and sounds great for $90. I recently bought one for my Senn HD580 and Garfish also just purchased one for his Senn HD600.

I have another thread started on Blue Jaspis where I will have to post more detailed info.