Will switching to a upper with a floasted tube help my 0-200 yd. accuracy any noticeable amount? I presently have a scoped A2 with 16" barrel and I wanted to go to a 20" floated upper. I don't use a sling and use my AR for hunting. What do ya'll think?

Probably not.  The increased sight radius going from a 16" to a 20" bbl will help your accuracy more than a tube.  If you're not using a sling, you don't have the problem that tubes were meant to fix - the sling tension deflecting the barrel.  

Well, you might notice a small difference, but I like to think of the floating barrel PART of a package. On top of the floating tube, you'd want at least a match trigger. The two help each other. From there, you could go with a scope, bi-pods, new pistol grip, etc, etc.

I decided  I wanted a free-float tube, but didn't want to hamper cooling, so I went with the FIRSH handgaurds.

The FIRSH handguards only costed me $100, and it gives me a free-float barrel, 4 way rail system, and cools the barrel quite well from what I've been gathering. They also look good!

So in other words, the free float by itself won't yield you large improvemnts, but if you can get more functionality (Rails, Cooling) AND a free float tube, now you talking about a worthy handgaurd upgrade.

BTW, the stock handguards do an AMAZING job keeping the heat away from your hands, you might find yourself wearing gloves after you install a standard free-float tube.