Obviously it depends on your level of income, but I can see three viable needs a rifle can fill. You could have an AR dedicated to long range shooting, a mid range carbine and a handy SBR.
I do think it's important though that you are intimately familliar with your go to carbine, whichever role your needs are most suited to. I imagine most people fall somewhere in between the mid range carbine and the handy SBR

