850W should be plenty unless you plan to run a peltier-cooling system (doubtful). A UPS is a separate device from the PSU. For those I'd have a google around for a decent review of one. If you have regular power cuts, prepare to buy new ones on a fairly regular basis. Frequent discharges don't do the batteries any good at all. The Xonar and a 5.1 setup will be fine. You could even use the onboard audio from your mobo without trouble.