Get a pair of DJ type speakers.IMO,in a business atmosphere,people are not that interested in how the music sounds.While lots of the speakers recommended above would be fine,why spend that much money on more or less,background listening.Just a thought.Good luck with you business.Here's a link to a site with a good sale going on.
http://www.cheapdjgear.us/Speakers_s/45.htm?gclid=CI389YrWqZ4CFQwJswodDFtdnA
http://www.cheapdjgear.us/Speakers_s/45.htm?gclid=CI389YrWqZ4CFQwJswodDFtdnA