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

To expand on the comment about a "transistor buffer stage", here is one way to do it:

This is a class B output stage and will introduce some distortion as it switches from sourcing current to sinking current, but it's sufficient for many needs. The current demand on the op-amp is divided by the transistor's current gain \$h_{fe}\$, and at your power levels there's probably not a general purpose op-amp or power transistor that wouldn't work here.

This schematic is from OPERATIONAL AMPLIFIER BASICS by Harry Lythall which has a section on audio power amplifiers with some additional designs for different needs, lower distortion, etc.

There is also a great amount of audio circuit information at Elliott Sound Products.

I have actually just recently built a small prototype around a dsPIC33FJ64GP802 that does exactly what you are looking to do.

I used a MCP6021 opamp (not an official "audiophile" opamp but it has a THD quoted as 0.00053% (typical, G = 1 V/V) rail to rail in/out and it's a pretty good all round part - it also has a mid-supply reference which is handy for single rail apps) driven differentially from the dsPICs DAC, and a TDA1517P 2 x 6W Amplifier IC to drive a smallish 8 ohm speaker (this is the weak link THD-wise - you may want to use a discrete transistor stage after the opamp, or a better quality audio IC)
Results were very good for my purposes, here's a picture (the board has since been hacked for other purposes but the three main components remain as shown):