My personal preference in the 46 class hasn't been mentioned yet, so I will. For anyone thinking about the OS 46 AX, don't discount the Thunder Tiger Pro 46. Its less expensive, but every bit as reliable as the OS, with equal performance. Put an 11x5 or 11x6 APC on the shaft and you'll be good to go.

Don't put the 46 LA on a Nexstar if you have another choice. Not knocking the LA. they're great engines. I have a Nexstar with a 46 LA because I had one sitting in the shop not busy and someone gave me the plane for free (I had to repair it). As far as trainers go, the Nexstar is one of the heavier trainers, and the 46 LA just doesn't have the oomph to fly it well.

Brad