To be fair when the 2400 came out it was being used with multiple monitors for gaming...
The resolution was just turned down, is all.
It's older now, but should still be able to run multiple monitors "okay" -- the problem is just that you can't game with 2.
You have to have 1 uninterrupted forward view. That means 2 monitors won't fly. You need 1 or 3 to game with (left, center right, thus retaining your uninterrupted forward view). Now THAT will take a bit more power than you have, and another monitor.