I've used the Knox products before and they do help with recoil - but they came on guns that I bought and I don't think I would buy them to add to any guns I have.
Is the recoil for the shotgun too much for you? If it is, I'd urge you to try a recoil reducer, porting the barrels, or perhaps consider stepping down to a 20 gauge. The most important thing is that you feel comfortable enough shooting the gun that you will actually go out and practice with it at least several times a year. Ideally, I would want a 12 instead of a 20 , but it won't do you any good to have a very powerful gun sitting in your closet that you never practice with because it's too painful.
If you are just starting out, you can buy light loads to practice with at the range, but, of course, you should ultimately practice with what you will have it loaded with so that the additional recoil isn't a surprise.
If you can, see if you can fire a gun with one of the pistol grip stocks - some people really think that helps with control.
If you are worried about overpenetration, you can get #2 or #4 shot and it will certainly dissuade anyone from advancing towards you at the ranges you are likely to encounter in a house. But, again, practice is key here so that you can feel comfortable hitting center of mass every time at indoor ranges.
Finally, the Mossberg is a very decent, reliable gun. I really like the safety on top feature so you can flick it with your thumb. I've used one for duck hunting and it held up to very serious abuse without failing.
Edited by drahthaar (03/12/09 06:09 PM)
Edit Reason: fix typo