Hi David,
I may be wrong (highly likely) but I believe the 6525 is the country specific variant of the 6535, one number is for the home market, the other for the export market but they are essentially the same card.
I'll go call a dealer I know and get some details if I can...ping me an email dave@opticalpower.co.uk to remind me in case I forget to come back here for a while.
cheers
Dave