Dvi vs d-sub

In the past the difference was greater, but dsub improved so you basically won't see any difference. If it has a dvi port on the monitor i would suggest using it though...(digital is just better  )

yeah there is a dvi port in the mointor

If you don't have a dvi cable then it probably isn't worth buying one then because the image won't improve much if any...but if you just have an extra laying around i'd switch it.