Welcome and it's great to hear another Armada buyer. The biggest set of rims you could get are 26". But ride quality will suffer. I suggest getting some 20's or 22's if you're looking at what size to upgrade. Brush guard isn't that good of an option, because suppose you get into an accident, the brush guard will probably do more damage to your car. Billet grilles are probably the most common item mainly everyone is doing to their Armada. It's all up to your taste for the billet brille. For AWD, it depends really where you live and you have to think about the conditions in your area (i.e. I live in Canada and my dad got AWD with the Armada, because of winter). If you're good with electionics then maybe you can get aftermarket equipment when it comes to NAV and audio. Overall i'm happy with the NAV in my dad's Armada. The BOSE isn't THAT good, but it goes...