Honestly, I would not reccommend wireless speakers. The sound quality is just not up to par with that of wired speakers. Plus, wireless speakers will be much more expensive than wired ones. If you are looking for sound quality and wireless, I would guess that you will spend more than $200.
I own a Klipsch 2.1 ProMedia GMX, and I've been extremely happy with them. I bought them for $150 about 2 years ago at the Apple store, but I don't think they sell them anymore. I've been thinking about upgrading to the JBL Encounter 2.1 speakers, which also retail for $150 at the Apple store. They match the white asthetic appeal of the iMac better than the Klipschs, but both provide excellent sound.