im in the same boat as you, i have never used monitor speakers because of their poor quality. in fact all the monitors I own don't even feature speakers. since you won't be using the speakers, DVI only monitor will work just fine for you.
image wise, DVI and HDMI give you the same quality image.
If your only going to use your monitor for your computer, then DVI is fine. However, in the future you may want to multi-purpose your monitor and use it for other input. For instance, I have my computer hooked up to my DVI connector, an XBox through the HDMI and a TV tuner through the VGA.