I NEED HEADPHONES....NOW

Firstly, I suggest going to headwize.com and you will find an entire website dedicated to headphones. Use their search engine (if it is working) to save time.
If you re-read most of the recommendations for Sennheisers you will find that most who like them use a dedicated headphone amp, frequently with tubes. The only way I have liked the Sennheiser 580 or 600 is with an Earmax. This combination sounded terrific, but is much more than $300.
I prefer Grado's but I do not wish to bother with a dedicated headphone amp. I have Grado SR-80's and RS-2's and like them both. I just picked up a pair of Denon AHD 750's to try for summer listening (when the air conditioner is on) and they seem to sound good for a sealed can.

I forgot to mention that you need to consider not only sonics but comfort when shopping. I use the SR60 earpads on both of my Grado's and I rest my eyeglasses on the earpieces of the headphones. Some other headphones do not work well with eyeglasses, some make your ears perspire, etc. If the phones fit tight initially, imagine how they will feel after an hour or three.

Prfront,
The reason I do not use a headphone amp is that I have tried 3 of them at home and have heard others at hi fi shows, etc. Only one amp, the Earmax, was better than the headphone output of my NAD receiver (this is my 2nd system) and the sonic difference was not worth the cost difference. Every time I get the urge to get a headphone amp, I take the money and upgrade my headphones, CD front end, cables, etc. I have heard the headroom crossfeed circuit and it is nice, and I may eventually get an Airhead as a toy to use with one of my Radio Shack 3400 cd players. I do not use a portable cd player for most of my headphone listening-I use digital separates that have been displaced from my main system.