I believe ever since they started incorporating HDMI ports on the card it has worked with sound. Because HDMI carries sound and video.
If you are building a computer for media purposes on your TV basically any card with an HDMI slot will work. I would go with something current because of reduced power consumption. So something in the 5000's or up in AMD/ATI and 400s and up nVidia.
If you are not gaming on that TV then go with something like a Radeon 5450 or a nvidia 610. Or kill two birds with one stone and get an APU and the motherboard will have HDMI on it as well. So you will have CPU, GPU, on one chip and just use the HDMI port on the motherboard. If you are gaming then it depends on the resolution you want to use but an APU would be acceptable or something like a Radeon 6670 and up.
as far as i know AMD started with the HD 2XXX cards having an onboard sound card.
Many early Nvidia cards uses a pass through for SPDIF from your sound card(HDMI was a merger of DVI + SPDIF, but has since become MUCH more).
Even my onboard(Intel HD 3000) has audio over HDMI. I just have to set it in the bios.
You are covered as bubbles11 says.
Even my old n cheap 4350(This thing just moves media center animations and video together[and not so well, but video on its own works fine]. a little more power is far better if you want the media center interface to at least be smooth.) works with hdmi audio.
This is $15 after the rebate. Doesn't get much better than that.
I still don't think you understand how HDMI works. It is video PLUS sound on one cable. If you have an HDMI slot, it can output sounds. You might have to enable a setting or two, but HDMI = Video + Sound.