Ok, I just listened to the ProMedia 4.1s at a shop this morning. They appeared to sound a little better than the v2.400's - which I own, but no way are they worth shelling out another $300 to upgrade if you already own the v2.400's.
If you don't own a pair of Klipsch speakers, then the 4.1's are the ones to get. If you already own a pair of v2.400's, the difference is noticable, but minimal, so stick with what you have.