Hi Hammer

Don’t compare Midi keyboards with Arrangers as far as price goes

Essentially Midi Keyboards are dumb keyboards, where all the controls can be programed to do whatever you want them to do (The limitation will probably be on what the module can accept)

Cheaper models tend to have less programmable controllers compared to the more expensive ones

If you are just using the controls on the module for your performance, then you will only need a basic keyboard to output note, dynamic and after touch information (Pitch and modulation wheels are normally standard)

If you want to use the controls on the Midi Controller to control the module, you will need to look at the Midi implementation chart (At the back of the module manual) to see what it accepts.

Here is a basic introduction to Midi to get you started http://www.tweakheadz.com/how_to_get_started_with_midi.html have a good read of it, and you will then have a much better idea of what you actually want.

Hope this helps

Bill