Each of the three terms used in your question is vague and need further explanation: power, voltage, current of an amp can mean a lot. Try to post a clear question.
The output power of an amplifier is the averaged product of instantaneous output current and voltage. To increase the amplifier's "power", at least one of both has to be increased. But there's obviously a difference between the actual output of an amplifier and it's maximum ratings respectively the limitations set by the power supply. So without telling more details, it's unlikely to get a reasonable answer.
Yes, but you still haven't answered the question : "Is it a single power op amp or an audio amp ?" or maybe its an RF amplifier.
You will also have to tell us something about its power supply, its load and the design of its output circuit. Maybe its power can be increased by raising the power supply voltage and capacity, by adding more output devices, or by providing a lower impedance load. And maybe not.
An incomplete question will not provide you with a complete answer!