Best way to connect PC to PA ?

I'm wondering how you guys connect your PC to your PA system?

I've made up a rig of adaptors and cables to go from the small connector on the sound card to a "pair" of standard quarter inch jacks... and plugging those into my Amp... but I'm getting a lot of noise along with the sound.

And... is the Sound Out connector on a typical PC sound card a 1/8 or 3/32 stereo female jack?

And the ultimate question... What is the best way to get professional quality sound out of your PC for a live rehearsal or performance?

Thanks for any help.