Benelli Sport II?

It would be much wiser to go with a Beretta 391 Urika. They are cheaper and far superior.

If you want a cryo-treated barrel go here www.300below.com
they'll cryo-treat your barrel for you. A Benelli is not a "step-up" they are great guns but just trick your Beretta out.
You can also buy a shorter barrel for skeet but it really doesn't make a diffrence if you shoot with a pre-mounted gun. If you shoot with a pre-mounted gun then you could easily shoot skeet with 34'' barrels.

New chokes are always great
Barrel Porting
Backboring is really nice
Having your forcing cone lengthened
Trigger work
Hi-viz sights
Having your gun fitted by a pro

Any of the above would be great for your gun.

Sorry, I misworded that. You CAN easily shoot skeet with a 34'' barrel (I have) but you have to shoot a pre-mounted and have to really be able to move the gun. If you have semi strong arms and know how to whip a gun-up it's really not that difficult. Again my apologizes for mis-wording my post.
Can you forgive me