Graphics cards HDMI outputs

Hello,

Recently I became interested in connecting my PC up to my 42" LCD screen in my living room when I noticed my motherboard had a convenient HDMI output on it. I got it hooked up, but anything intensive is very slow because it's using the limited onboard video capabilities of the motherboard.
I have a much better ATI 4800 series card sitting in a PCI-E slot, but it lacks the HDMI output. So I am considering buy a new card that can do HDMI, but I am wondering how audio would get from the PC to the TV. HDMI carries both video and audio signals, which my motherboard was able to do because it processes both - but the video card is not responsible for audio. Do these video cards with HDMI outputs accept audio signals and pass them through, as configured by some sort of BIOS or driver setting?

Thanks for the remarks.

you can bitstream audio through hdmi v 1.4a

my gts450 does, i believe you can also bitstream audio through a 430 gt which is a good home theatre pc card are you trying to game on this computer or just stream video?

i really don't know... i kinda always assumed it was just pulling the audio stream from the mobo audio and passing it through the pcie as an upload into anfor export out the hdmi ... but to be honest thats what made the ost sense to me, there could be an audio driver on the cards i suppose. now i am curious and hope somebody does answer this