As to EAX - it's become a little ambiguous . . . any game that uses OpenAL can technically claim to support EAX. Although I'm sure to use the EAX image and all they must pay some kind of royalty for it . . .
OpenAL pretty much includes EAX 2.0 extensions, and the EAX 2.0 SDK is free, IIRC, and the OpenAL SKD is 100% free. So, any developer that feels like using these audio extensions can get away with it, and technically support EAX (although it might no be EAX 5-HD).
Take STALKER: Shadow of Chernobyl, for example, it supports EAX and Open AL . . . but only EAX 2.0.
Oh, and on the headphones . . . it's a little rough to recommend something. Altec Lansing makes some good headsets, some of the 5.1 headsets are great (if you're willing to pay for them) . . . theres just so much on the market, though . . . just make sure to do some reading before making a purchase. Look up reviews, look if other's have post their opinions, etc. Take it all with a grain of salt, though, not all users who share their comments on a specific product might have the "ear" to really back up their statements - same goes for reviewers as well. I see a lot of reviews for speakers, etc where they're reamed by users for stoopid reasons that have nothing to do with output quality nor build quality.
- obviously petrol didnt cost you too much otherwise you'd probably paying the equivalent for the other XFi cards that are bought localy/online.