I'm building my first AR-15 and definitely need some advice here. My Lower is PSA its already assembled with FDE Magpul parts and what not( Palmetto State Amory). I'm looking to get the parts from Palmettostatearmory.com
(Im going to also use a PSA Upper also) I have a charging handle and auto nickel boron BCG already!

My needs are a 16" barrel with 1:7 twist 5.56mm . I do like the stainless but IDK how it'll look with a FDE Parts. So I was looking more at the CHF barrels. I wanted to put a free float 10-12" rail system? (something that covers the gas block of a Mid-length) but I'm not sure how much all that will cost seeing I have to buy the tool and upper receiver holder. (If I need to i will buy them though, I'm getting the building fever and want to build more!)

1) First off I want to know if a stainless is actually better than a CHF ( Chrome moly vanadium barrel is actually the least of the three correct)?

2) Would a 10-12" rail system be fine for my need or can I go a bit shorter and be fine with that gasblock?

3) Is it the same price or more to build a complete upper and barrel with what i need or is it cheaper to buy a complete with just a regular grip system and buy a free float later.

Considering these for the price and adding free float later. Are these good deals? OR SHOULD I BUILD THE UPPER AND HOW MUCH ? THANKS IN ADVACE

http://palmettostatearmory.com/index.php/ar-15-05/barreled-upper-assemblies/psa/5-56-nato-223/psa-16-mid-length-stainless-1-7-freedom-upper-without-bcg-ch.html

http://palmettostatearmory.com/index.php/ar-15-05/barreled-upper-assemblies/psa/5-56-nato-223/psa-16-chf-mid-length-premium-upper-without-bcg-or-charging-handle.html

First off when I started to build my first AR I knew that I intended to build many more so I bought all my own tools (mostly all replaced by better quality tools). I have built over 115 from scratch and done depot level work on several hundred more. First welcome to the fold (read... addiction) of building custom AR-15s. Second these are my opinions crafted over many years of working with these incredibly functional and versatile weapons system nothing more.

To answer your questions:
1) Stainless vs chrome-moly (Actually a steel alloy including chromium & molybdenum)
Stainless is more a visual and maintenance thing that anything else. If a chrome-moly barrel is properly maintained (oiled and cleaned) then there will not be any noticeable difference in longevity or performance. Don't forget though that stainless can also corrode and rust if neglected I have picture if you would like to see.

2) For a 16 " carbine barrel a 9" rail will cover all but the longest gas blocks.

3) One way or the other this will came down to having the tools, I'm not trying to avoid answering the question but the cost of the tools may direct your choice. In light of this you might want to get a low cost upper built to you specs (PM for links)

This is not intended as comprehensive list but just the basics:
AR-15 Armorer's Wrench
Upper receiver clamshell, Action block, or Geissle reaction rod
Torque wrench
Forward assist Roll Pin punch
White lithium grease

Good kit to get you going BROWNELLS - AR-15/M16 CRITICAL TOOLS KIT