Tough decision, aramis.

Yamaha PSR S900 is most feature reach (and expensive) of all.

Yamaha PSR OR700 is one step down from S900 with specific features for oriental music (styles, sounds, scale setup).

Roland E60 is in the same class as OR700, but have 76 keys keyboard (all others are 61 keys).

Korg Pa500 is in the same class as upper two, it's "little brother" of Pa800 (PSR S900 class Korg keyboard).

Soundwise, You have to listen to each of the keyboards discussed, and then make Your own decision. That's the main reason why You can't depand on other peoples opinnion, because manny people get used to the sound (or operation work-flow) of specific brand, and (strongly) dislikes other brands.