Make sure you get your rifle chambered in 5.56 in order to be able to shoot both. I'm a big fan of AR's, and you should be able to find a basic unit for under a grand, although with goodies it can get quite a bit more expensive. I've been pleased with my Bushmaster M4gery, and also heard good things about Rock River Arms.
There are also AK variants out there that have been chambered in 5.56, or Galil rifles, not sure about prices on those though.
They do have more "tactical" (for whatever that word actually means, I don't personally like in its current usage) Mini-14's with pistol grips and adjustable stocks and rails and whatnot.
If you go the AR route, make sure you get as many of the options you want on your initial purchase. Like I wanted a chrome lined barrel, 5.56 chamber, adjustable stock, 16.5" barrel, flat top reciever, ect...