Yes to both. Amazon takes international cards for everything. It's necessary to use a forwarding service though for something like a laptop. Amazon themselves only ship books, DVDs and Kindles internationally. Some of those that sell through Amazon might ship internationally. It's certainly the case for the UK Amazon.Have you bought a laptop from Amazon before? With a South African credit card?
Now of course Amazon might look askance at someone overseas who has never ordered from them before wanting to buy a $1000 item with an international card. But then they'd not be alone in that.