If anyone is interested and asks here I will detail the steps by which I succeeded in installing the Xtreme Music card on Windows 8 x64 Consumer Preview.
The consoles and control panel work and most importantly I can't hear any difference in the card's performance on Windows 7 x64. (I don't 'do' digital or optical connections, only analog to a fine old set of Cambridge 4.1s.)
The one problem remaining to be solved is that all settings made either in the Creative audio control panel or the consoles are retained only for the active Windows session and lost upon reboot or the next cold start.
I have tried running the consoles with administrative privilege and messed around with permissions for various folders and some Registry keys, all to no avail.
Very grateful to learn if anyone has insight to this situation on Windows 8 x64 CP!