if ur 460 still works, you can have them both, r9 for ur main card and 460 next to it, only for physics..
As for the PSU, the recommended is 600 and toxic needs some extra power... I dont know! If you end up buying one, get 850w psu, for feature upgrades, such as crossfire. And here is a suggestion http://pcpartpicker.com/part/corsair-power-supply-cmpsu850hxEdited by Orifiel - 11/6/13 at 11:55pm