I'm with the others here as far as being careful shooting that stuff out of your nice Benelli. You don't want to take a risk messing that up for something that is going to most likely disappoint you anyway.
I've never fired any of that stuff through my gun, but I've seen some of the videos of other people doing it on youtube and it doesn't look like the results are worth the excessive prices they charge for that stuff.
For the price you'd pay for some of that stuff you could get a bunch of different kinds of buckshot or slugs and do some patterning or shooting for groups and learn some more about your barrel and what it shoots best. If nothing else, it's additional real-world training that will benefit you more and probably be a better way to utilize your resources.
Of course, if you watch the videos online and you absolutely want to test out some of that specialty ammo then I'd suggest, as others have, buying a low-cost single shot break-open to use as a dedicated "special purpose" shotgun.
I don't agree with the name-calling and childishness that some have demonstrated here. Often in these forums a high post count seems like a license to do exactly what moderators ban or edit most new users for. Just asking about specialty ammo doesn't make you a mall ninja or constitute trolling or anything like that.
In fact, some of that specialty ammo (like the "Pitbull" buck-n-ball loads or the "Rhodesian Jungle Load" of large and small pellets) have their roots in real military history. I think most people get ornery about discussing this stuff because they believe (and maybe correctly so) that those rounds have been proven less-effective in real-life combat situations.
For instance, the US Military supposedly started out using those Flechette loads in Viet Nam, but then found that the little darts often hit the target sideways because the tiny fins didn't stabilize them correctly. Since they were ineffective the military switched to 00 Buck and that turned out to be brutally effective.
So my thinking is just that some people are of the opinion that it's stupid to go "backwards" and waste time messing around with technology that has been proven ineffective or less-effective than current favorites and that could have the potential to damage your gear.
I agree that it is cool that you can actually get so many different types of ammo for the 12 Gauge shotgun and that's one of the things that makes the shotgun my favorite weapon of all-time. I used to want to get my dad a Remington 870 Marine model to stow in his boat locked up with a box of flares and buckshot. I thought that would be a neat way to utilize the shotgun. I think I've even seen rounds that launch some kind of line across to other boats in storms, but those might not actually be for 12 gauges.
Another neat use of the shotgun is for shooting "bird bombs" to scare bears away or to clear birds off of airport runways.
My only point in all that is just that if you can really come up with a scenario where you can justify using some kind of specialty ammo then by all means try it out (being careful to test in a low-cost gun first if possible). It's great for creative users to have access to so many options, I just think some people take offense to all the marketing "HYPE" surrounding these types of loads and that is probably where some of the hostility is coming from.
Take care, be safe, train hard and have fun!