Thanks Starkeeper, Bart and others for your feedback.

I'm far from an expert but I asumme that compared to external amplification/speakers the built-in audio-capabilities (be it 10Watt or 5Watt) will be a compromise anyway.
In that respect decent integrated sound is good enough for me ... if I need more I'll hook it up to my Krell/Wilson-Benesh gear ;-)

This will be my first keyboard and I still need to learn a lot. I don't see myself moving around with it, a PC is nearby and I don't have any legacy floppy material.

Also I got confirmed that the EXR keyboards behave like decent midi-controllers with ACID, Cubase and the likes.

Summing this up I'm going to order an EXR-3 + Edirol UM-1SX (usb/midi interface)

Can anyone of you give me some direction for good books, software, Web-sites etc. for beginning keyboard-players ?
b.t.w. What does this so-called 'music assistant' function do ?
Would I be missing the ability to edit styles any time soon ?

Looking forward to sharing experiences with you all.

Cheers,

Louis