Wouldn't you be speed limited by the lowest bandwidth equipment in the mix? Unless it's fiber (or equivalent bandwidth) from end to end you're not going to be able to go faster than what the slowest machine will process. If your outbound bandwidth is limited, you may want to compress files locally first, to save on transfer time. That being said, 64-bit scp will probably work fine? If there's no restrictions, making it a torrent would probably work as well, if you need to transfer them more passively.