The K5000 series have been very badly marketed by Kawai!
They have their own unique additive synthesis method- they sound like nothing else out there!
They are very capable synthes but you wouldn't use them as your one and only board- not even the K5000W with it's extra general MIDI sounds.
They work great with other synthes and they look good too!
Their are strong at sharp digital and also have a 'dirty' sounding analogue quality about them- but I'd hardly call them 'warm'.
They excell at movie soundtrack type evolving pads, organs, synthe basses and 'RockGuitar' is the meanest sounding distorted guitar sounds I've heard from a synthe!!!!
The first versions of these synthese had some strange operating quirks and the factory sounds were crap also. But subsequent operating system updates improved things considerably- including the factory sounds. They are now up to Version 4.
They are very powerful synthesizers and the deep additive synthesis system is very hard to fathom- but the results are well worth it!
Buy one if you are into something that sounds different from the pack- they are a bargain at the moment and they will be a sought after classic instrument one day!!!!