I have been thinking about donating since this is a really nice server, with all them custom plugins and friendly people. But i have enough money to donate its just the fact that it is recurring every month... which will end up costing more than most games i play...
Try BunchOfBadger's guide of when buying supporter: http://empireminecraft.com/threads/guide-when-buying-supporter.19234/ Its under 'Purchase' for the information you want