Suggestions for reasonably priced speakers for MBP

All -

I'm stationed in Afghanistan and have limited space - obviously my home system isn't with me.

I'd be grateful for recommendations for some reasonably priced, reasonable sounding powered speakers. Source is a 15" MBP. Price range - anything up to around $300-400.

Thanks in advance, and apologies if this has been hashed over to death - I'm somewhat time-limited and was not able to do a detailed search.