Is is possible to use audio from the HD 4870 through HDMI for my monitor audio and use audio from a pci sound card at the same time?
can i have PCI audio for my Headset and the HD 4870 audio for my monitor or can i have audio for my headset just communications only and the other audio like from my game or music come out of my speakers?
Windows will default sound to whichever sound adapter you set it to, now applications can also have sound adapters set to them if you have more than one, but its dependant on the software you are using..
for example, Lord of the rings online passes sound through my 4870 over hdmi onto our 48inch plasma surround system whilst I have my mike set up on the creative soundcard, so yes it is possible application dependant!
Actually you can't. Windows can't handle, in fact I dont know of any particular OS that can output to more than one sound card/sound bus at the same time. You can set up particular programs to output audio by default to certain other programs if thats what you're on about but not simultaneously.