I don't work with speakers, so I'd have no idea what the specific criteria would be without googling, and I'm too lazy to do that. I do recall you will need a current-limiting resistor, as under certain circumstances in their normal operation, speakers can act almost like shorts (well, more like saturated inductors, which have some parasitic capacitance and resistance, but its low enough that it will allow too much current to pass through in most circuits)
HOWEVER, I do know about op-amps.
Foxpup is right; the output voltage will never exceed the powersupply rail voltages. In fact, because op-amps are semiconductor/ICs, they experience a fixed voltage drop (Actually dependent on multiple factors, ranging from semiconductor choice to temperature, but its 'fixed' in that its ideally independent of the actual properties of the circuit) (where the power supply voltage is greater than the drop, or a drop equal to the power supply voltage when it is less than the maximum drop) on the output from the powersupply inputs. So if the negative PSU rail was -5V, and the positive PSU rail was +10V, the maximum outputs might be something like -4V to +9V. if you had +.5V and -.5V on the power supply, you'd end up with an output range of 0V to 0V.
Also, its important to note that the op-amp has a maximum voltage rating on the power supply rails, for example, +-18V. You'll want to check the datasheet for the specific model of op-amp you have, or else you might fry it.