I have all expansions but 2 from the previous site, yet it still wants to charge me 29 euros to upgrade to gold subscription. Even 'upgrading' to silver would cost me 18 euros, and I already have everything offered in silver and much more. Shouldn't it be very cheap for me to add adventures and empires instead of 29 euros?
The default setting for buying subscriptions is until 1 year from now. Your previous subscriptions are valid until the end of this year. If you use this date, also upgrading should be only a few Euros.