Define your budget and purpose: Weekend plinker? Varmint hunter? Service rifle competition? Fighting carbine? SHTF/Carbine class/serious use? If money is not an issue, I'd get yourself a Colt first and foremost. With a ceiling of $1500-2,000, my pick would be something like this:
1. Colt
2. LMT
3. Noveske
4. LaRue
5. Smith and Wesson
6. Charles Daly Defense
7. Sabre Defense
8. Armalite
9. CMMG
10. Stag
11. Bushmaster
Thats just an opinion formulated on some pretty decent research. You could also have a builder like our own John from JDL Sales, or Jon Kruger at Anvil built to suit....