I can't tell if you can put a scope card in an xpander chassis at all (meaning: there _could_ be a generic uad card plugged into a slot inside, or a custom board could be hardwired to the pcie bus as well), but somehow I would expect no.
EDIT: in the manual for the Xpander they say:
The UAD-Xpander contains a UAD-1e card that looks similar to the UAD-1e model for desktop computers. However, the cards are not the same! Do not attempt
to install a UAD-Xpander card into a computer slot, or put a UAD-1e into the Xpander chassis. Doing so will damage the cards and/or the computer logic board.
so the xpander is basically an express card to pcie adapter, and you would not be able to plug a scope card into it, since it is pci not pcie. nevertheless you cannot plug any other card into it without risking the card or other peripherals or even the mainboard.
with a magma (provided you connect it with cardbus) you will most probably experience performance loss, as reported here. if xou consider using an Xpander you have an express card slot (in favor of cardbus) any, haven't you? I don't know anybody running a scope card in a magma that hooks to a pcie x1 or xpress card (where I would expect somewhat higher pci performance), but I'd like to hear about it. volunteers, any?
with scope 4.0 you will, btw, not be able to run your scope card with vista. you need to purchase the upgrade to 4.5 which includes 5.0 (being the first release compatible with vista).
-greetings, markus-