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I'd choose the AV40s personally, but you're never going to get a particularly fantastic sound out of anything that cheap. Look to spend around double that and you'll get something which more than quadruples it in performance.

For example, the Alesis M1s, which will make the ProMedias look like a rip-off.
 
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I have owned both.

Games and movies > Promedia 2.1

Music > M-Audio AV 40

Promedias also have some quality issues sometimes
 
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