Hello Lionstracs
All OAS instruments as from November 2005 came as standard with OAS 7.
OAS 6 was introduced in early 2004.
I have included a link below where you can download a free magazine which shows the history of the OAS system, it also contains details of OAS 7. (Please remember the magazine is about 12 -18 months old and further updates to OAS 7 have become available)
In addition I have included a link where there are some screenshots of OAS 7.
OAS instruments up to OAS 6 used Cubase as the VST Host, where as OAS 7 has an integrated VST Host.
The sound system uses custom (All connections are internal) Creamware Pulsar/Pulsar 2 DSPs, which have 32 bit processing.
Due to being busy at present, I have not yet had the time to upgrade to OAS 7, but I will try and put together some more details of the differences between 6 & 7 when I get back from work.
Hope this helps

Bill
http://www.worldofoas.co.uk/sample.htm
http://www.yourhobby.nl/forumorgel/viewtopic.php?t=1195

Update
The magazine site seems to be down at the moment so I have uploaded a copy to Rapidshare.
http://rapidshare.com/files/3447870/World_of_OAS_1.pdf.html