Looking for recommendations for sound card and headphones

Currently i work online only, so when working I watch movies or listen to music on my 2nd monitor. I work with a very loud fan so the quietness doesn't matter.

I am looking to turn my computer into more of an audiophile headphone type system just to get more out of movie watching and music listening while plugging away online.

Currenly I'm running with a Grado 80i $99 headphones, Raeltek audio on my motherboard and a $25 filo amp just to boost the sound on certain things that I download that have poor quality.

For music, I have no preference, besides whatever people recommend. Currently listen to a couple albums of elton john, queen, ozzy, eminem, snoop dog. But I watch tv shows and movies way more than listening to music (only time I listen to music is when I need both monitors to work on and planning on picking up a 3rd monitor for this case).

I have no interest in gaming on this computer (if I'm gaming I'm not working, if I'm not working I'm not making money), and right now I just download what I can, but planning on upgrading to a blu ray drive for even better quality movies. Will never use a speaker system so only headphones.

My anticipated budget is $600:

1. Headphones?
2. Soundcard?
3. Amp?

I seen some soundcards with built in amps for about $200 that seems to be recommended. Would it be worth picking up one of those and spending $400 ion a good headset? Or buy one of each? And any recommendations?