At the risk of starting the Evangelical Equipment wars, might I suggest you take a look at the Korg Triton Classics. This will give you a totally different sound which will complement your Yamaha sounds. Also, the prices and availability of expansion cards such as the MOSS and EXB Sound cards allow you to expand the Korg into a full blown synth as you mature with the product.

Get to a music store and try some of these synths. This is the way I went as I have the Tyros and the Korg Triton Pro with EXB Piano, Studio Essentials, and the MOSS Z1 Synth card installed. To me this is a dynamite combination for performing.

Regards,
Al