You have to decide this for yourself. You monitor will upscale all inputs to it's native resolution, whatever that is. The only way to know is to buy a player and try it.

As a very general rule, monitors are fair at upscaling and fair to poor at de-interlacing. But unless you're willing to spend the money for an Oppo player, or an HD or BD player, it's not worth considering an upscaling player as these are the only players that are really good at it. There are far too many DVD players that upscale poorly, most of them in fact.