I wouldn't go higher than the .61 because it is an ARF and because it is a CMP ARF. The airframe may not be able to handle much more than that.
My choices?
Magnum XLS-52 / $89.99
Tower Hobbies .61 / $89.99
Thunder Tiger Pro .61 / $129.99
O.S. 55AX / $149.99
O.S. 61FX / $159.99
My top choice of these is the Thunder Tiger Pro.
There are also the Evolution line of engines but I have no experience with them.