Hi Jupiter4
You say you are prepared to go to high end arranger Keyboards, well although more expensive then the boards you mention, consider the Wersi Ikarus & Lionstracs Media station, as these are software based and you can install VST plug-ins (Soft Synths etc) of which there are many available for all the types of music you require.
Media station probably has the edge at the moment, but with Wersi OAS 7 software due out soon, they will probably be similar, both (Wersi with OAS 7) can also use Giga samples.
Whichever board you get, I would you suggest you get a copy of Style works 2000, which will allow you to covert styles from various keyboards to the one that you own. (Some fine-tuning will be required to get the best results)
With Wersi instruments (And I think also Media station) you can install the program directly on the keyboard.
As an additional point Wersi use OEM versions of the Creamware Pulsar 32 bit dsp cards, and so can accept samples designed for these cards as well as Akai samples.

Bill