If you want action as real as possible to the real piano, you may not want Casio. Yamaha is the closest you can get to the real thing, although the P70 uses different keys to the famous P250 graded keys (which is the standard of all digital pianos in terms of touch).
Since you mentioned that touch is a higher priority than features, I will suggest leaning more towards Yamaha. Roland also has lower end digital pianos (the ep series also with build-in speakers). The only problem is Swee Lee don't usually stock them, so you can't try them out before buying them.
I will not go for the Prokeys at all. The touch will probably be the worst of them. They are aiming at lowest possible cost, and so had to sacrifice a number of things, one of them being the touch of the keys. Furthermore, there are so many reports of inconsistencies with the velocity of the keys with their Keystation Pro88 that many returned their units to M-audio shortly after purchasing them. The Prokeys88 probably uses the same keys as the Keystation Pro88 - unless somebody has more updated news about it.
