Hammer - as you may well know, I have a G70 and think it is an awesome arranger and keyboard. But to answer your question I would have to say that the S900 looks to be the best bang for the buck. Yes, the Tyros 2 is around 30 lbs and does a lot more than the S900, but I feel my money would be better spent on the S900.

Now, I have played neither, but owned a 2k and 3k. Knowing the OS and the added features on the S900 and Tyros 2, I might spring for a S900 before a Tyros.