OK, fine, I'll give you a little more service than that. Just for you, readers, I reached up on my shelf and pulled down my WoW box to compare the old system requirements to the new BC ones. Interestingly, the expansion does call for a little more RAM (512mb, 1gb recommended) than the original game does (256mb). The original box doesn't say they require a Directx sound card, but apparently the expansion makes that distinction for whatever reason. On the Mac side, while the original game required OS X 10.3.5 or newer, the expansion calls for 10.3.9 or newer. I don't run WoW on my Mac, but I believe all the 10.3.x updates came free with System Update anyway, so I'm sure you'll be fine.
And even if you don't match up to the recommended specs, I wouldn't worry too much about it-- Blizzard's games are very forgiving on the hardware (not so much when you're running a full AV or MC, but when you're soloing in Hinterlands for sure). Then again, if you do need new RAM, now's the time to start looking.