Just ignore AG, he does tend to sound like a broken record.
It appears the PAM series ICs are just about all there is for high efficiency amplifiers 5V operation. There are many sellers on amazon & ebay etc. [Correction - see below].
For the cost, it may be worth trying one to see of it works OK and the quality & volume are acceptable; theoretically you could get near 1W per speaker, which should be OK for desktop use.
The amp modules are very cheap it's a simple experiment to do a lashup test, and the only real way to really know if one is suitable for your needs.
I've built an amp for my PC but using higher power amp modules based on the TPA3116 D2 IC; I've used quite a few different amp modules containing those, from ebay, and never had any problems. Some run my whole-house audio system.
You do need a separate power supply if you use these, though; 12V or higher (up to 24V.) [No, again see below].
These are examples of common boards I've got; there are loads, from numerous suppliers.
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(I have three of the first style in the PC amp, plus a separate surround audio control PCB; a bank of the second style are in the house audio, after modding to directly access the balanced input on the amp IC).
The second one claims to work down to under 5V; I never noticed that before, but I was not looking for low voltage ones.
I've just tried a spare module at 5V from a little test rig regulator, and it is surprisingly good - enough volume to be annoyingly loud with speakers close to you, I've not got it near full for a comfortable level.
The little reg board uses linear regulators and has a 12V supply in to it, so at half an amp it would be dissipating around 3.5W of heat (and rather warm). It is staying stone cold, so the amp operating current is quite low.
The only small speakers I have to hand are a couple of tiny bare ones ripped from some scrapped cheap PC speakers years ago; it's a bit tinny like this, too much treble & not enough bass - but I think it would be fine with the speaker in suitable enclosures.
(The old minidisc player was the only thing I could think of to get a 3.5mm audio source next to the other parts).
It's good enough to leave on for background music while continuing to type !
[The MD player had the Deep Purple "Under The Gun" album in it when I dug it out].