The headphones will definitely be a major improvement and will aid your game. If I recall correctly, they are a simulated surround sound. Knowing which directions footsteps are coming from is a huge advantage. This assumes Ghosts has a typical IW sound set and it is not the terrible sound set used by 3arch in Blops2. After an adjustment period the Scuf will pay dividends as well.
The new internet connection may help and may hurt, depending on IW chooses to treat connections in Ghosts. In blops2 you had an advantage by having less bandwidth than needed to host and more than likely saw lag compensation work in your favor in most lobbies. If Ghosts is more like MW2, you're going to be better off, if it's like blops2, you're gonna be worse off.
As far as additional items, get good cables and if you're looking to replace the box tv, look for 2-4 ms delay to keep from getting additional lag from your tv and if it has a "game" setting use it.