Theres some excellent points made here. Over time, a lot of people here have tried to get me to (completely) empty my wallet on a pair of RS-1's or CD3000's, but I have been reluctant to because of the rest of my system.
My philosiphy with headphones is the same as with speakers. You should choose a pair that is appropriate to the rest of your equipment.
I did not really want the CD3000's or RS-1's in my system, because part of me feels like I wouldnt be doing them justice, and without trying to sound like a snob, I think the equipment I am using is considerably better than what you are using, and yet I still dont feel like I'd be getting the best out of the high end cans.
If you are interested, I am using a Rotel RA-01 speaker amp and Terratec EWX24/96 soundcard. IMO, this £250 amplifier and £130 soundcard, whilst outstanding products in their price class, I suspect might not do the utmost justice to a pair of £400 or £650 RRP cans like the CD3000 or RS-1. I am actually using a fairly modest (but once again outstanding product for its price) £90 pair of cans with this setup, and I feel like I have struck a balance. The sound I am getting with these headphones is likely to be better than what 99% of anyone who has ever heard a headphone would have ever believed possible.
What am I trying to say? Its not about having the most expensive setup, its about SYNERGY - the result is greater than the sum of its parts. If you spend your money wisely, then you can have a kick arse setup (including the Audigy if you like). Remember, its not JUST the cost of the headphones you should take into account, but the cost of everything you will need to get the best out of them. Source, Amp, Cables, and believe me, it quickly adds up. The CD3000's are not merely a $400 ticket to audio nirvana, but a merely a single piece in the jigsaw that will most probably cost considerably (think double or treble) more to get the most out of them.
Say for example, your Audigy is worth $50, and the CD3000's $400 thats $450. However, $450 can buy some still very good headphones, and a far superior source for example. What will sound best? I'd put money on the well chosen good quality source and headphones over a really good pair of headphones and a source which hasnt been properly considered or thought about.
Anyway, thats enough from me, I've just babbled on a bit!! Just a thought though.