I would suggest an alternative route for you. Since you are relatively young, I hate to see your creative abilities tempered by an arranger keyboard.

I would suggest you get a Yamaha Motif ES. This keyboard will have a great Piano patch for you to hone your core piano skills. It will have a killer sequencer with a new technology called a "Phrase Factory" which will essentially allow you to create killer arpeggios and Multi-Pads. The Motif will have the Mega voices of the Tyros and Killer Synth sounds. YOu will also be able to sample your own sounds.

With the Motif and the 740, you will have the best of both worlds, but the Motif will allow your musical ability and creativity to expand past your 16 years. I also think the Motif will be slightly less expensive than some of the other arrangers.

I really think the Synth approach will force you to be more creative and develop your own grooves, your own sounds, and your own "style" of music.

Al