I agree with Treo, in that the army can take activities that sound like they should be fun, and manage to take all the fun out of them.
I doubt there's any significant difference between manufacturers and models of ARs in cleaning them, when the exception of big changes, like the piston-driven models. To be perfectly honest, I continue to be impressed by the AR design in its simplicity and versatility.
I think you will wind up wanting at least a few rifles. Maybe not overnight, or this year, but your interests are a bit broad for any one rifle to cover. Most of us agree that AKs and ARs are two different ways of looking at doing the same job, meaning intermediate powered rifles intended to give high-volume of fire with reasonable accuracy at short to medium ranges, using a meduim sized cartridge in order to be controllable by most users. The AR has a bit of an edge in controllability, accuracy, and ease of use, but at the same time, it's probably a little bit more accurate than it NEEDS to be for a rifle with this purpose. I recommend that you go to a rental range and try a few. Most people find they are genuinely fun to shoot, and don't hurt you. When you buy one, I strongly recommend getting one chambered in 5.56 mm rather than .223, they are NOT exactly the same, the 5.56 is more able to shoot the other than vice-versa.
Bolt-action rifles are a bit more accurate, but you will need to shoot a lot before you will see the difference. The higher-powered options you are looking at would probably be covered for now with a good, name-brand used 30-06 bolt rifle. (Remington 700 is where I always start.) Look in any pawn shop. This rifle will serve you out to 800 yards. You can use this for everything from varmints to elk.
I THINK, to need or want anything bigger means you are trying to hit something at a range an '06 can't go to, and/or something an '06 can't kill. The magnums, .50 BMG, .416 'Feinstein', etc, are honestly what you start using when you have maxed out your abilities with .30 caliber rifles.