AR is a great platform. I have a PSA I bought the upper kit for and assembled the lower and a Stag model 3 I bought complete. Neither had great triggers but both were acceptable.
I did the PSA trigger on my own and it came out very nice. On the Stag I opted for a JP Enterprises trigger kit.
Like I said both have great triggers now but the JP was a much easier install and took less time since they had already done most of the engineering.
My wife - a shooter also, tells me my PSA with 20 inch barrel and a little more weight than the Stag kicks a bit less. Personally I like my Stag better as to me its much lighter and I'm old and can carry it easier.
To the OP buy a flattop receiver as you can put a carry handle on it if you so wish but you can't take off a permanent one...
If you are looking at putting on a scope, I know it isn't cheap, but the Burris P.E.P.R. mount and Leupold Mark AR scope is THE combination on these rifles in my opinion. GOD I love that scope!
Pappys Rifle Shop