Hi and welcome to the addiction.
Here are a few thoughts on buying or putting together your first AR-15. I'm far from being a guru, but I have been down the are buying block once or twice.
First, as hard as it is, for a first time AR buyer, you must divorce all of the "I want that particular feature because it looks cool or scary", from your decision making. You need to be worrying about relibility and hitting what your shooting at. Not about things like, if your muzzle brake looks cool.
Do not get any barrel with a faux flash hider that is simply for looks and hangs a piece of metal on the end of your rifle that has no function at all.
honestly, many of the functioning muzzle breaks out there, serve no purpose other than to put something on the end of the barrel, that sort of looks like a flashhider, because many AR buyers just can't get over the fact that the that thing on the end of the barrel "looks cool"
I've shot a lot of 16" barreled AR's at night in my life, most of them before the ban, and to tell you the truth, I never saw a flashider of any practical config, that I thought was worth a d**m or that would hide the fact that I was shooting an AR-15 at somebody at any range.
Once you start shooting AR's you will also discover that, there is little need for a muzzle break, since 5.56 does not generate much recoil in the first place. Again most of these are on the ends of peoples barrels, because they look cool.
Most muzzle breaks out there on the market, make the report of the rifle, much louder, Bushmasters AK brake is particularly known for this. Many breaks also vent gas directly out at the shooters on either side of you at the range, which can be particularly annoying.
While it may not look cool, that plain old crowned heavy barrel, that looks so much like the barrel on you dads bolt action hunting rifle, is about the most accurate thing to ever come down the pike.
As for Middy's, This is a config that I am very fond of. No they are not set up like Dissipators, with the second gas block., they use a Mid-lenght gas tube that runs directly to the gas block you see sitting at the end of your handguards. Most middy's are produced by Rock River Arms and Armalite, if you simply must have chrome lined then your choices in middy's drop to Armalite only.
Armalite's Middy Barrel weighs less than Rock River's Middy, due to the fact that Armalite mills the barrel down to a mid-wieght under the hand guards, this is probably a good thing, as Rock Rivers Full Heavy under the handguards is pretty heavy as 16" barreled rifles go.
Me I would just by a Middy from one of those two companies, rather than fool around with some sort of barrel conversion, just buying one would be alot cheaper and less hassle in the long run.
I hope this helps you out.