I own an ego 08 and personally, I don't think it needs any upgrades. The only thing I would recommend getting... is a TechT iFit Barrel Kit or a Smart Parts freak kit for a better paint to bore match, and because the stock barrel on an Ego is .693
Just to give you an example, most paint I have come across is around .685 (the smallest I've shot is .677) and a better paint to bore match will effectively increase your accuracy. Imagine shooting .682 paint through the .693 stock barrel and it becomes a mess. Your paint will fly in every direction. Now imagine shooting .682 paint through a .682 barrel insert, and it shoots that much sexier.
Kush provides the best performance. It ups the FPS the most, meaning you can lower your HPR the most and make your marker even more efficient. It also has the soft tip which makes it easier on brittle paint.