Between various stems me and my buddies have used, we found the Thomson to be the most dependable and the stiffest. The new style, X4, has a better steerer clamp design, although I've never had issues with the standard, you just have to grease up the threads on the pinch screws.
I ran the CNT MonkeyLite XC. Perfect width, good up and back sweep. Light, strong. I went of some good sized drops, in the 4 foot range, with those bars and had no issues.
Seat post. Don't even try to consider a rigid post. You've gotta get the Gravity Dropped, simply gotta.
Pedals are tough. I love a lot of things about my Mallets, but I've broken the wings, the bearings haven't been reliable, and the metal pieces that bolt on to front and rear are totally mangled and the screws have always come loose. The ejection mechanism, inherent to the egg beater design, is very frustrating, especially when your cleats are not new. I ran Time Z platforms for a while and found the retention mechanism a lot better. I have a lot of bikes with crank brother pedals on them, so for the time being I am sticking to the Mallets, but they are far from perfect.