1100 is a great semi-auto skeet gun. If you got the 11-87 you could always pull double duty for hunting, unless your Benelli has a 3" chamber.
Anyway...Brownell's, Cabela's, or Midway should have all the choke tubes you need. The ones that are extended and knurled go for about twice what the flush chokes do.
Cabela's 4 Choke PackMake sure whatever 1100 you get is outfitted with the Rem Chokes.
That 4 piece kit above should be enough for a mid-level shooter.
I get by with S/S IC/IC M/M F/F and use them in differing combos on my O/U Berettas.
Carlson's make a little better quality tubes than Remington, but they run $30/tube.
Carlson's TubesIMHO, Briley makes the best non-compensated tubes they also run about $35/tube.
Briley Skeet TubeI have shot the X2, it was a tad bulky and felt a little cheap to me. The 1100 and 1187 fell like they are finished better.
Skeet is more about rhythm than speed. That X2 and Benelli action are great for hunters and Sporting Clay pros who need following shots on unknown distance and speed birds. For skeet, they are known distances and ranges the faster cycling is moot.
HTH....
Ed