Besides ..all of the above...You may want to consider a laptop, running a host like Mixcraft4 or Forte...Mixcraft 4 comes with an assortment of VST's (sounds), and loops..

You can add OnemanBand10 and/or Livestyler to use with any Yamaha style..OMB will also allow you to edit styles..

You will need a USB keyboard controller..Your total cost will be considerably less than the moderate to high end arrangers (under $1,000)..

This method will handle what you want to do today..and take care of your future needs too..