I want to improve the sound of my iMac with external speakers so I bought Logitech Z313 2.1 rig. These sound like only a minor improvement over the iMac's internal speakers. After reading speaker reviews I have settled on the Alesis-M1 Active 320 desktop monitor speakers that cost $99.99. These use USB 1.1 to connect to the computer. Does anyone have these speakers? Will USB speakers work on an iMac without problems. Is there a better choice in the $100 price range?