Any card that uses the Broadcom chipset should be a goer using the bcm43xx driver yes?
Yes and no. When it comes to playing with the bcm43xx, not all Broadcom chipsets work well. Probably the most prevalent example of a poorly supported Broadcom chipset is the 4318. To be honest, if I was buying a new card, I would probably avoid Broadcom based gear. They offer zero Linux support and apparently couldn't care less about Linux.
If you're looking at cards, Intel chipsets seem to be well supported, but the bottom line is that on a G4 machine you must
get a card with native Linux support. Ndiswrapper is simply not an option here, so be sure to do your homework on this.