Well depending on what you had planned for your rifle I'd recommend a Colt Canada MRR 11.6 for CQB (or just about anything actually).
A CC MRR 18" when wanting to reach out a little farther or a DPMS Recon G2 in .308 if you're wanting to knock down those metal plates with a little more authority (yet still be similar to an AR-15 sized package).
Of course if you were after a NR AR (not that we actually have that option for us civvies in Canada) then perhaps a nice ACR with a larger calibre barrel... upgrade for hunting... Perhaps even an ATRS Modern Varminter for Coyotes and such...
Otherwise a DD in any flavour wouldn't disappoint; as others have said a KAC would do quite nicely and generally holds the top spot of AR mastery although some may say different...
Les Baer's have one of the best accuracy guarantee's at .5 MOA, if that's your thing; plus I've heard nothing but high praises from fellow GunNutz that shoot them.
If I were to choose a Piston AR platform a HK MR223 or MR308 would work well although they might come in just a tad over your $3,000 price point.
Personally if I were somehow awarded $3,000 to spend on an AR I'd get one of those Colt LE6933 Commando's for sale from a site sponsor right now, actually make it two since they'd likely come in under $3,000 for the pair. Why, well for me they are the epitome of AR'ism and just look awesome, plus they'll shoot forever w/o needing much, are like Lego for gun guys and gals (what AR isn't) and in the right hands they can still do it all and well.
Otherwise I'd fall back to me all time favourite which is basically any product from Colt Canada. Why you say, well because when the world turns nasty and you just need an AR that's going to work each and every time you pull the trigger, while providing extremely good accuracy with anything you feed it CC's are great.
CC's do all that while maintaining one of the best reputations in the world from the Men and Women who work with these in the field day in and day out too.
Cheers D