I'm confused too. I think I may have missed something - I should point out that I don't see obobski's posts because I got tired of him trolling and posting bogus info repeatedly.
E.M, if isolation isn't a big thing, there are 3x DT990 up on Head-Fi FS/FT for $125CD to $210 right now. They'd...
$1.9M is obscene, unconstitutional, or just f@#&ing nuts. $54k is sane. $500 is reasonable.
To be more specific, $1.9M is a strong-arm abuse of the legal system as a weapon against lower socioeconomic castes.
Right, so, how is it relevant that all existing sound cards use one of a pool of ~3 DSP chips? (exaggerating somewhat, obviously, but not by that much)
1. Your card is still more than fine.
2. The answer is always to wait as long as possible (or very nearly always). The cost of the card you want to upgrade to is nearly certain to come down, and it is nearly certain that your super awesome upgrade target will itself be one-upped.
The Swans, of those you listed. Bass isn't going to be great without a full subwoofer, which would eat your whole budget on its own. But it should be better than most options at that cost.
DT770s are used on Head-Fi FS/FT for roughly $100-150 all the bloody time. If you're patient, an awesome deal. I think they also surplus some models to eBay occasionally.
If this is primarily / exclusively for headphones, Xonar Essence STX is basically the big dog. There are a few other...
DT770s, and if you MUST have digital 5.1, just use CMSS-3D. You'll have a dead solid platform, and you can turn the 5.1 part off and on as desired.
Although at that, there are better things to drive it with.