A couple of thoughts...
Head over to the Maryland AR-15 site and look at the recommendations page. Good solid advice for buying an AR. Then I'd head over to the industry forums on this site and ask Fulton Armory, Armalite, and others what they would recommend based on your needs. They all have forums over there, and most will "build to suit" the upper of your choice.
I'd be tempted to go with a 20" HBAR flat-top. I'd have the barrel fluted. I'd have a fold down front sight, (since you said you didn't want one,) and a fold down rear sight, or just use a removable carry handle. Then you could take off the scope and use the rifle with iron sights for plinking, self defence or whatever.
The flat top receiver gives you lots of options. Be sure you know what you want before you buy. Otherwise you'll end up like the rest of us with a safe full of AR's in different configurations.
Oh, and welcome to the boards.
Edited to add -
Bushmaster will put their Varmit free float tube or their V-Match tube on any of their uppers. And the Maryland AR site is at
www.md-ar15.com