One of the advantages of HDMI over DVI is that it not only carries a digital picture, but also digital audio over a single cable. The other poster (I'd have to see the post) was probably trying to tell you that if you used an HDMI to DVI cable, you would get the video, but not the audio signal. You'll need a separate audio cable for that.
Do you have just the TV, or will you have a surround sound system? To get the Dolby Digital 5.1 from HDTV, you'll need something capable of decoding that signal. I use digital coaxial cables (audioquest) for my audio to an AV receiver. You'll have to double check this because I'm not positive, but I am under the impression that in order to get Dolby Digital, you need to use either a Toslink (optical) or Coaxial digital cable. Both are digital signals directly from the source to the decoder.
Whatever you decide, remember the phrase garbage in, garbage out. Don't invest in expensive equipment without using decent cables. They don't have to be super expensive, but you do want quality. Other forums are probably better suited to helping you select what you need.