$300 is a pretty small budget IMO. In that price range, I almost think going with a wireless speaker (there are many) but similar to the Jambox, Cambridge Audio Go, Sonos Play:5 might be the best route. With that said, my Big Jambox sucks when there are too many competing bluetooth devices around, so I would hesitate to recommend that unless you were going to plug the audio source in directly.
If I were going for value I would possibly shop around on the buy forum at Audiogon. I got some PSB Imagine B4 Bookshelf speakers there for $150 shipped, and I just checked and they have a Cambridge Audio integrated amp for $250. But with cables, interconnects and shipping even that basic set up with approach $500. And if you want to add an Airplay feature, you'll have to pay another $80 for an AppleTV unit (refurbished).
I guess it might be easy to walk off with those portable bluetooth speakers though.
k.