If you have listened to any XP roland keyboard and don't like the sounds, don't get the JV module. They are the "same" sounds (pretty much, patch lists sometimes are different but the base "raw" waveforms are the same in the XP keyboards and JV modules.)
You sound like a true "korg fanatic" so I would stick to what you like.
Personally I love the Roland sounds, recently bought a XV-5050 module (the XV voices contain all the JV's PLUS new patches and all kind of extra effects, over 90 of them, and software to edit and create your own patches.)
I studied the Korg Triton Rack and Korg Karma before making this Roland module purchase, and I much prefer the Roland sounds, so really, it is a matter of personal taste.
I think the Korg sounds are much more for "today's" music (dance, trance, hip hop)where as the Roland sounds are more for classical, and old time pop and rock and roll. Exactly why I shyed away from Korg, I am an oldie but a goodie!
hope that helps,
Cathy