Yeah I was talking GPU wise, the CPU could last up to even 10 years from now in terms of gaming, if it's not going to die for some reason.
You may add another 280 if your MOBO allows.
My current mobo is an entry level one. If I ever decide to go for a crossfire setup in the future, I'll change the mobo.
If you didn't buy that PSU yet you could afford to tone it down a bit and save some extra cash. Really you don't need more than 600w if you don't plan on using two cards.
I have already bought all the components. The CPU is a real power hog (or so I heard) at 125 watts TDP, and the specifications for the video card mentioned the power supply requirement as '750 Watts'. Hence I went for an 800 Watts PSU. I knew it might be overkill, but at least I don't have to change the PSU if I ever decide to go for a Crossfire setup at some point in the future.