Its always best to replace the brakes of the Armada with slotted and drilled rotors. Having said that, the brakes of this car are not that bad at all. Try driving a LandCruiser and slam the brakes and you will know what I mean. Its a terrifying moment not knowing when the car will stop. My rotors are worn out (have to replace them shortly) and they still stop when I want to. I also want to mention that I don't do any kind of towing.
I used to drive a 1st Gen Dodge Charger before this and let me assure you nothing eats brakes quicker than that car. I used to go to the dealer every two weeks (yes, two weeks!!!) to get it replaced under warranty, till I just gave up. The boss was starting to suspect something fishy. What was the point anyways? The brakes were crap.
Anyways, the point that I was trying to make is that, why would you want to purchase expensive unreliable brakes from the dealer when you could have 4 rotors + pads (enough for both axles) shipped to you for under $300? This goes not only for the brakes, but also for other stuff that your car needs. There is a sponsor on this site that will get you everything cheap. Also, you can try rockauto.com and everythingnissan.com. I've personally bought from all of these guys and my personal favorite, everythingnissan.com cant be beat in international shipping prices.
If you are seriously considering a 04, take her out for a the test drive and check the suspension and handling, knocking sounds from the dash, the exhaust manifolds, the overall condition of the exterior, the fog lamp assemblies and the tire conditions. You definitely don't want to spend money on the exhaust and tires right after you bought it.