I second Ridley25. With a tank that long two filters might be useful for several reasons. First, more water circulation, and both ends get filtration. Second, if one filter goes out on friday night of a three day holiday, you're still (partially) covered until stores open. Third, multiple filters mean multiplying your options for media to meet conditions. So if phosphorous goes up, there's room for phos-sorb, etc.
Only having experience with the 2217's I would recommend them. Also, all previous posts about using at least 2 of them are right on target. If you are planning on getting fish as juvies and letting them grow in the tank 1 may be okay to start. But, you will most certainly need 2 sooner or later. Good Luck.