Just in case you having a hard time getting enough energy on target (ie doubling your .470 NE) I notice Bertram has the first Sterling Davenport .585 Nyati for $5,000 on the site. Just the ticket if you need to stop a charging Panzer.
http://bertramandco.com/rifles-for-sale.html
http://bertramandco.com/rifles-for-sale.html