To my knowledge, you need a small "riser" board to be fitted to the Iyonix so it can take podule cards.
Whether the podules actually work or not depends on *if* the podule's ROM module is 32bit compliant. If that's the case in *theory* it would be possible to free up a PCI slot by fitting the Castle USB podule in removing the onboard USB PCI card (assuming of course RO5 don't get too picky about the kbd being on a different USB card from that originally used).
You should note that the USB PCI card (although currently used in USB 1.0 mode) can support USB 2.0 (once someone get's around to writing a USB 2 stack for it). So I'd be inclined to keep the PCI one.