Looking for chain and sprocket advice.
 

My Yamaha Banshee chain is stretched to the limit, so it's time for a new set. I'm trying to decide between steel and aluminum sprockets. I know steel lasts longer, but aluminum is lighter. I ride mostly trails and some sand. What do you guys run? Also, when you shop bikes for drivetrain parts, do you usually buy kits or piece it together? Looking for the best value without sacrificing quality.