The minimum power requirements they give your from their site is assuming that your using the cheapest, biggest, piece of crap PSU ever made. Your going to buy a decent one, cheap ones will blow up your entire rig. This is very similiar to the one I use, mine just has more power, and a different out side because it is badged as an XFX.
Most people will warn you against Rosewill PSUs, but I've never used one so I can't say for certain. I can say I've never had an Antec fail on me. And generally I like the 80 Plus certification so it's more efficient.
If you're not seriously overclocking, you can run a 660 on a good 450W PSU. You just have to make sure it has the PCIe power cables for the card.
Unless you're going for multiple CPUs, you rarely need more than a good 500W PSU.
So i want to get the Zotac GeForce GTX 660 video card. Would a power supply with maximum power of 600 watts be enought to power the minimum of 600 watts needed by the video card?
The GTX 660 in general only requires a 450W power supply according to the Nvidia Website: http://www.geforce.com/hardware/desktop-gpus/geforce-gt...
The Zotac (as a non reference design) MAY take a little more power than this (I cant tell as Zotac's website is terrible and they don't say) but i highly doubt you would need 600W to power it. If you get a good quality power supply from Corsair, Seasonic or silverstone then they will have greater efficiancy and a better warranty. Cheaping out on the PSU is not a good idea.
In answer to your question, a 600W GOOD power supply will be more that enough to power your CPU, Graphics card, All your fans, hard drives,an SSD if need be etc. If you are considering SLI, get a 700 - 750W power supply for the extra card (notice how it did not add the 450W requirement on to 600W? that is because that number accounts for all of your components) a 500W will be more tahn enough for your situation, My current rig is running on a 450W generic no name brand (pre built unfortunately) and it powers a Zotac GeForce 9600GT (a similar level, mainstream graphics card when it came out in 2008) with ease.