did you read the datasheet for the op-amp ? If so you would see that its not going to give 40-50W output. Its a very low level output.
for the power level that you require you are probably best to use at least a 2 or 3 stage amplifier so that the gain is evenly spread across all the devices and thereby retaining stability.
Have a look at some of the Mitsubishi power block modules, the RAxxxxxx series. They have a wide range of modules covering different frequencies and power levels.
Most will operate to full power out with ~ 100mW input.
Dave