Get the Model 1 standard CAR kit for $400, and an Eagle or Mega lower. With shipping, $517 to you (more if you have to pay trasfer/shipping on the lower...I didn't). BTW, Quantico Arms has the Eagle lowers back in stock TODAY, according to an email they sent me. $100 plus shipping. I've seen the Megas for $89 shipped, and if you can get the Oly for $82, jump on it.
In the long run, I think you'll be happier if you get the flat top; you can always snag an inexpensive red dot or scope on the EE., then replace it when you can afford something better. Even a $30 BSA red dot would work for a while; you're not gonna be happy with the limited sighting options of the A2 config, if that's gonna be you're only rifle for a while.
My 16" Model 1 just did a bunch of sub moa groups with the loads I was testing...first chance I had to put good ammo through it. I don't see you needing a 20" rifle; the 16" standard barrel will do everything you need it to, and be lighter and easier to track with.
The M4 profile is cool, but I don't think it gives you anything special, and I think the M4 kit will be more expensive...stick with a standard barrel with no muzzle device. Down the road, if you want to swap the barrel or install a float tube or whatever, you won't have to worry about removing the muzzle brake.
I'm VERY happy with my Model 1 standard CAR kit. I've pimped it out some, but still, the basic rifle has performed flawlessly ever since I got it. I'm happy with the accuracy so far; I'm gonna tweek the load I worked with this weekend some more, when I can afford more bullets lol, so I expect I can really get it dialed in to do sub moa all the time.