Wow, most of you guys scored above average!
Yeah, I don't think sound hardware is that dependent - I just put mine there if it actually did have any effect.  I believe they have to produce samples at certain frequencies, which this test only requires.  I think what differentiates better sound systems from poorer ones are stuff like jitter, dynamics and frequency range.
Though I'm not sure if there's an effect at lower frequency differences.  I seem to do fairly similar on my $2 headphones that I bought for the hell of it one day (and sound so poo poo that the PSP's clicks sound screwy).