Audio Amplifier Op amp
There are several power op amps, and also audio amplifier ICs, which would meet the stated requirements. However, this approach may be overkill for the kind of fidelity likely from the signal generation source.

As mentioned in a comment to the question, adding a transistor buffer stage is perhaps the best way to achieve the desired results. 

Also, do note that a dual-rail (+/- x Volts) supply at a relatively high voltage is needed for these op-amps / chip-amps. While the dual-rail requirement can be circumvented with a suitable virtual ground implementation, voltages involved are still not your run-of-the-mill logic voltage range.

In any case, to answer the question...

Some suitable Op Amps:


PA85: High voltage power OpAmp - Obsolete, I think, but still sold. This used to be a classic.
OPA541: High Power Monolithic OpAmp
OPA549: High-Voltage, High-Current OpAmp
OPA2544: High-Voltage, High-Current dual OpAmp
NE5532: Low noise dual OpAmp


Some suitable Audio Amps:


LM3886: 68 W continuous average output power into 4Ω at VCC = ±28V
LM3875: 56 W continuous average into 8Ω
LM4780: Stereo 60W, Mono 120W (parallel-able) Audio Power Amplifier