I've had a look through your previous posts, and got the impression you may be going to be disappointed.
You seem to want an amplifier that runs on 5v and outputs 20W.
Straightforward Ohm's law says that (1) that requires 4A from the supply, and (2) the speakers will have to be about 1Ω
(1) isn't impossible, but most speakers I've seen are 4Ω so (2) will be difficult
And that's not taking into account the fact that sound isn't DC.
For a sine wave, the peak voltage and current is almost half as much again compared to the RMS value, and the peak power is twice the average.
So your supply will have to be able to supply ±6A
So look for a supply of, eg, 24v and an amp capable of handling that.