The real bottleneck is the internet which is 10 or more times slower than the 100 or so megabit LAN.
Bob
I use the Slingbox Pro HD to sling Seattle Seahawks games to my son who is in the military and moves around a lot.
I now use a cat5e from the Slingbox to my gigabit router behind a gigabit modem, he signs in to our Slingbox account and watches the game.
I was told by a tech at a computer store that I should be using Cat6 instead on Cat5e as the picture will be much better on my son's end.
That doesn't make a lot of sense to me so thought I would check here to see if that statement is true.
We both have Comcast and are getting about 55 down and 11 up on both ends so bandwidth is not a issue.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic