okay now crossfire or wait a year and upgrade and tell me that PSU will do the job
Yes it will, because
1. his motherboard doesn't support SLI, not to mention just replacing the graphics card is more sensible than hunting down a matching 960 in three years.
2. even if he switches to a more powerful GPU in the future it'll likely not use much more power than the 960 he'll have, and as I said he still has power to spare.
Either way, a 500W Corsair CX wouldn't be an upgrade over the 450W XFX; the XFX has either the same or more power on the 12V rail, better parts quality, higher specified operating temps (30°C vs 50°C) and a longer warranty.