Do I Even Need A Soundcard? Options

[humbug]

Hi there, I'm a newbie. I just threw away some money on an Edirol UA-30 USB audio interface which sucks and is WAYYY too noisy. I did a side by side test with running sound straight into my minijack (on a G4 Powerbook) and the sound was sooo much better.

So... why do I even need a soundcard? I've heard that M-Audio makes decent devices, but to me they look just like the cheap, plastic piece of crap I just bought. Is it just that Edirol sucks? Did I get a bum device? Are other devices that much better? Any help is greatly appreciated. Thank you.