Does your picture look bad? The best way to optimise the image is to choose a resolution closest to your screens native resolution. You won't be able to do that with an HDMI type connection though, so if the image looks washed out, you're best swapping
to a HD-VGA cable.
I use a monitor, and the VGA on my LG monitor looks better than the HDMI on my LG HDTV. Both full HD and 22". Make sure your monitor is high res (720p or 1080p). I actually bought my monitor for £110 and it's brilliant, who says gaming has to be expensive.