I'm looking for a mid-range arranger keyboard that I can afford, and here in my country there aren't many alternatives.

The only i-series available is Korg iS50. I've heard that this has already been replaced by the newer iS50B, but I don't know what's the difference between the two. If it's a big difference, maybe I'll ask the dealer to bring it in.

The other alternatives are KN1600, PSR640/740, PK7, and old Kawai Z1000. I'm personally leaning toward Korg's and Yamaha's.

Maybe some of you out there could make the distinction much clearer to me. I would like the comparison between iS50 and PSR640 since comparing iS50 to PSR740 would be much unfair...

Opinions about the other models at this range are also very welcome.

Thanks
Poonna