Hi Vikki
The Wersi version is called the EX1.
I have included some links to details, Demos and the UK dealer below.
Bare in mind they are not cheap, however because they are software based instruments you do not have to change them every 2 -3 years to get the latest technology, and so in the long term they work out cheaper.
They also have the advantage in that they can use Akai samples and VST instruments to allow even greater expansion.
http://www.4shared.com/file/28662846/503c24d0/Wersi_Open_Art_System.html
http://www.boduns.starlink.ru/MUSIC/DEMO%20SYNTH/wersi%20oas%20EX-1%20v,7,0/

UK Dealer http://www.harmony-music.co.uk/organs.htm

Hope this helps

Bill