IMO, the 850W would be more than enough. But it also depends on how much you have on your desktop. I went for a 1000W psu for my system, just in case. :)
Try opening the application via the Start Menu, it might just get it back there on the systray. It may not also be one of the apps that run on startup.
Have you checked the BIOS option under Advanced\Onboard Devices Configuration if the HD Audio is enabled? you might also want to check Device Manager if there are unknown devices and such, one of them might be the audio device of your board.
IMHO, it doesn't really matter what board you pick. I guess all of them have good/great on board audio with multiple jacks, it all depends now on what speaker/head phone system you'll use.