I think you may want to reconsider your criteria, and I want to add to the note of some of the other guys here. If you want a "rifle", something with distance performance, power, and different from your pistols and shotgun, then you shouldn't be looking for something in a pistol caliber. Its not hard to choose between ammo, or pick the difference between a rifle and a pistol caliber.
With your price range, I wouldn't consider an AR. In my book, an AR is meant to be reliable, decently accurate, and really not practical for anything but warfare and shooting range plinking. And you won't find a reliable one under 500 unless your really lucky.
I have not had much experience with pistol round rifles, at least none with any good accuracy. Most seem to be safari protection/ survival guns to me.
For 400, you can get a good bolt action savage in many different cal, like .223, .243, .22-250, .308. Then choose what you want to do. Small, med, or big game, or just a paper killer. How far do you want to shoot?
I mean, even though some do, I doubt you will be putting a decent scope and shooting to 400 yards with an ar or pistol cal rifle, or even half of that. To my knowledge, and I may be wrong so don't flame me, but pistol cal rifles always came off to me as survival rifles. If you want to break your norm, and get something different, get a standard rifle cal, and put some lead far down the range.
To me, there is nothing better than making 400 yard shots on a gong. The fire, seconds of delay, and the clunk in return. It is much more satisfying that the bang bang bang of pistols. Your not shooting something, but sending something. Sending it far, and exactly where you want it.