DVD-A's would be easy, as they are supported by Power-DVD, just get a copy of that and a good multi channel sound card and off you go...
But for SACD's... Since the transport format is proprietary, you can't just play or rip them... I suppose you can connect the output of your SACD player to the input of your sound card and record them and then create a file that has all the channels, but there is no standard way of doing such thing and you would have to deal with sound fidelity degradation.
-Jeff