with 80k attachments you will waste time mostly on transferring the attachments, the network delay will be your killer. If you can avoid importing attachments at all that will probably be the best, and after the WordPress is setup you can try to find a plugin that scans a directory and creates attachments for its file (sorry forgot the name of it).
Otherwise set your staging wordpress in the same LAN as the source sever.
In any case I remember reading that amazon AWS services have relatively slow disk access times, so you might better get a powerful VPS from companies that bill by the hour. I think rackspace do that.