I've done a lot of reading on these cards. To sum up:

1. There are some big differences from the Audigy. How much difference they make to your ears is probably both subjective and dependent on your speakers/headphones. But I'd guess the difference is bigger than between the Audigy & Onboard Sound.

2. There's also a measurable difference on the help it gives games (at least some) and this might get bigger.

3. X-Ram is all going to depend on support. At these prices not very many people are going to buy the cards with X-Ram on. But I suspect that once OEM versions come out, and maybe a version with X-Ram but no breakout, that may change.

4. Breakout box. Just can't see the point myself, very little use and lots of extra dosh.

5. 24-bit Crystalizer: opinions seem divided on this. Some reviewers think it's the best thing since sliced wotsits, others that it sucks the big one. The median opinion is that it enhances certain areas, like percussion.

My feeling is that, if you have an Audigy, it's not worth the money at present, unless you have money to burn. Wait for the prices to drop/OEM versions to appear/see what the X-Ram takeup in games is.