I am currently living in USA and have bought 2 external HDD's here for use with TM (and to hold my audio as my 160Gb internal is way way way too small for me). When I get back to Australia is it safe to plug them in? Just with an adapter? Or can I even just use an Australian power supply? They are Western Digital MyBooks 500Gb. One is USB only, the other is Firewire aswell. Thanks!