paulyshore wrote:... I want to upgrade things on my current car and try to increase the value a little....
when you say "increase the value", do you mean make it worth more to sell? or worth "more" for you personally

IMHO, cars/trucks such as the Pathfinder/Qx4 are not vehicles that appreciate in value - unless you trick it out, but the amount of money (not to mention time, effort, labor, stress) you may spend to trick it out may not compare to the selling price/worth.
If just for your personal appreciation (ie. you plan to keep the truck), I'd go with suspension first. Looks are one thing, but building off of a solid foundation (pun intended) is top notch in my book. A car/truck may look ragged-y, but when that car/truck beats me in the turns or handling-wise, the hat-tip goes to the other.
One thing I want to mention about the K&N (or any re-usable air filter) is the chemical used to catch particulate. I've heard experiences from some K&N users that the chemical can sometimes drip into the air-intake and gunk up the MAF sensor, causing some engine idle stumbling or irregular engine performance in general. It's relatively simple to just pull the MAF and spray some cleaner in there to clear out the gunk, but I've never really heard any significant performance gains over OEM air filters. But again - this is probably more of my opinion than engineering-fact.
Another potential upgrade is manual locking hubs (if you're 4x4 capable).
Some claim MPG improvement, while I haven't seen any significant and consistent MPG improvement in my WARN manual hubs, I tend to go along with the others in saying that the manual hubs' benefit is reducing wear on the transfer case and front axle (CV's, front drive, etc). Others' experience in off-roading will say that a benefit is that you can unlock the front CV axle if you somehow damage the front drive.
I suppose what you want to do or what you want out of the truck depends on the direction you want to use your truck - Offroad? Daily/city driving? Car/Truck show? Speed/racing? Track?