"I have read your guide on how to use an HDTV as a computer monitor and found it to be very informative. There is however one detail I am unsure of. This is Sound. If I were to plug my PC video card to my HDTV via a DVI/HDMI cable I would get pure digital visual but no audio correct? But if I were to plug it in via HDMI/HDMI from video card to HDTV would I get audio? Or do i have to buy a sound card with HDMI out to get surround sound?"
There are a several different ways to get audio passed from your PC to your HDTV. Depending on what hardware you have available, you may be limited to stereo audio, with a few cases where you can also get surround sound.
Stereo audio from PC
Stereo audio is going to be the most common scenario, because there still aren't many source video files you'll find online with multi-channel audio. Many HDTVs include one HDMI connection that also has stereo audio in via RCA connections, which would simply require a mini-plug out of your computer to the RCA connections on the TV, in addition to the cable for video.
Surround sound audio from PC to HDTV
If you have an HDMI video card that also includes audio support, you would get audio passed to the HD screen similar to what's available from any other video device. This is considerably more expensive than merely working with what's already in your system, but gives you something closer to a "real" home theater experience.
In most other cases, you'd need to pass audio from your PC to a home theater receiver with support for surround sound, while passing the video separately from the video card. You can find home theater receivers for under $200 that will give you acceptable surround sound specifically for this purpose, which is still cheaper than overhauling your computer to support audio over HDMI.