If I were you and had the money I would buy a Mediator and Voodoo. Even a "lowly" Voodoo 3 3000 is more powerfull than the cybervision as it includes more option of Hardware acceleration than the Cybervision.
Also the Mediator has drivers for variuos great PCI soundcards, 10 and 100mbit ethernet cards and Even TV cards (which you can plug your 4000's composite output into and play classic games in a window on Workbench!!)
