Battery powered 4W amp

It occurred to me, for a small very clean amp, this is the place to look. I have not been here for a while, so my stack of schematics is a bit OBE.

Anyway, I am looking to build an amp for speaker testing. Getting the power noise out of any of my full size amps is quite a task, so something battery powered is possible but not required. My smallest amp on hand is 60W, and not handy for portable and takes up too much space on the test bench. I only need 4W or so, but I want it VERY flat, 5 to 30K. I don't mind high feedback to get the distortion down to the .001 range as it is not for music listening. Something silly like 10 op amps in parallel would probably even work. Not eloquent design. Any threads to point me off to here while I troll around to catch up?