Definitely.
If you're going to buy the RG11 parts, then you'll want the crimper, the compression fittings, and the ground block (since the RG6 ground block "may" work, but it will be a tight fit). They also make barrel connectors and various other style connectors that allow you to splice your RG11 to RG6, which you'll want to do before it enters the actual set top box - although you may get away with shoving RG11 into the connector, I'd pay the few bucks more so that you don't damage something or bend something so that it causes you problems if you ever need to use RG6 in the future.
You dont need any special 'barrel' or ground block or splitters a regular barrel will connect RG6 and RG11, the "other end" of them are the same both 7/16 in size. For RG6 and RG11.
I'm thinking Lumpkin666 was referring "congestion" a person would have on a dual groundblock if they used RG-11 fittings. Things may be too tight to adequately tighten the fittings down. Hence the RG-6 to RG-11 splice-jumper idea.