i have the center diff adapter. there is no difference from stock. but i do use the qoncepts split diff set up bought this aluminum piece for longer wear.
for bearings both tko and xtreme have good kits. but the best bearings are Acer ceramics. they are on tower hobbies for like 79.99. entire package. i think they are worth looking at. its gonna be my choice when my bearings start to give.