Well, DVI (digital) and VGA (analog) definitely have a quality gap between them.
Im pretty sure that digital just gives you better response time by the graphics card, as well as it is on high quality machines to deliver more pixels at a similar or faster rate than VGA.
I am suprised that you do not see a quality discepancy or response time discrepancy between DVI and VGA on your dell 19 inch LCD.
Also, just as a a note, Stereo sounds better to me than mono sound
