>>107130140
>>107130318
Creative Labs is probably the best sounding, in that size.
Edifier has some small size speakers, but I haven't tested it. I just know the cheaper they are the shittier they sound. Even their expensive speakers sounds average at best.

If you want to go a bit bigger, 5.5"(W)x8"(H)x7"(D) then Swan OS10 is nice. It's what I use.