For powerDVD audio, should i choose waveout, spdif output, or directsound?

[Anaconda]

I have the Hercules Game Theatre XP, and labtec pulse speakers

 

[whitelight]

i think the spdif or directsound will produce the best sound. i have an aureal sq2500 digitally linked to midiland 7100 plus speakers, and i can't tell the difference between the two.