The best AR/22 Upper is Tactical Solutions, but they are kinda pricey. I've had three of them and they are awesome....one I converted into a dedicated AR/22 SBR. I've also had a Chiappa Upper, but I didn't like it as much. The TacSol Uppers are very lightweight and shoot great.
Top is 5.5" Tactical Solutions AR/.22 LR with SSparrow