Yeah. I've got mine in a modern-ish case that doesn't have a very good beeper, and it's stilling on the floor, so games that use it sound like butts.
I wonder if the speaker signal could be converted to a standard headphone jack to go in the line-in jack.
You can do that no problem, just link Speaker Out on the motherboard to a Line In on the sound card (the one you're not using for your CD). PC speaker is mono, so you may want to sent it through both channels.