Moe,
the Yamaha PSRS900 would be a great alternative to your Tyros2. It is much lighter and shares almost every feature. And, because you say you love your Tyros2, there is no reason for switching to something else onless you are unhappy. I would though suggest that because you are looking for something less expensive and the 900 sells in the $1,500 or so price range (I don't know how this fits into your budget), you might also consider the PSRS700 or even the PSRS500 as alternatives. These keyboards do not have all the features like the 900, but still sound very similar to the Tyros2.
The Korg PA50 is a good keyboard, but unless you are unhappy with your Tyros, getting a keyboard with 60 note polyphony(PSRS900 has 128), floppy disk drive instead of USB device and host is probably not a good solution for you. Korg is replacing this keyboard with a PA500 in the very near future which will provide USB and more polyphony.

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George Kaye
Kaye's Music Scene
Reseda, California
818-881-5566
www.kayesmusicscene.com