Quite a few cards are capable of connecting to your Digital Receiver and
producing glorious STEREO. The problem is that A3D and EAX signals wont be
up-mixed by your receiver to multichanel output. You may be able to get
Dolby Pro-Logic to do some up-mixing for you, but the results are usually
nothing to shout about when compared with real 5.1, 6.1, 7.1 audio.
Regards EAX, this is the King of the hill in terms of positional audio at
the moment, the problem being other than Creative's cards the support on
most cards is limited to EAX 2 which is no where near as nice as the later
EAX variants available to Creative owners. Also, non Creative cards tend to
pay a greater penalty in CPU cycles when producing EAX output.
There is a third option though, in the form of Nvidia SoundStorm equipped
motherboards. While the quality is not equal to the latest of Creative's
offerings, it does manage to output the SP/DIF AC3 signal that would allow
you true surround sound output from your PC to your Digital Receiver. To
the best of my knowledge there are no other Consumer PC sound solutions that
will output the required AC3 signal to your Receiver.