Tires for 2014 Sportsman 400 HO

Ive got a 400 HO that has been working great with the stock tires, but I think it needs something more aggressive for the mud. I think Maxxis Zillas would look great and do good in the mud, but how do they compare to ITP Meyhem or Mud lites? Would it be safe to run 27s or 28s on my 400? If so would I NEED a clutch kit? Any other problems I would have to watch out for running the bigger tires on my 400? Any feedback helps!