I had a 660W Zalman PSU and it fried, taking my video card with it, meaning that I have to replace both.
I went to the repair shop near my house and had a little argument with the technician there. He insists that you never need more than a 500W PSU, I insisted that I needed a 600+ for my rig. He swapped out my broken 660W for a 500W for me to try it out and he also swapped out my Zotac GTX 460 1GB and gave me a 9600 GT to use until the parts come in.
My current specs:
Some generic 500W PSU
Asrock P67 Pro 3 mainboard
2x2GB Gskill 12800 RipJaws DDR3
300GB SATA 7200rpm HDD
Temporary: GT 9600
With this rig, my Nvidia 9600GT drivers are giving me a warning message saying that there is insufficient power and that the graphics card has been turned down performance wise as a result.
Now, on Monday my parts are going to come in. I'm getting a much bigger case with four fans, the biggest PSU the computer guy can find in my city (a Gigabyte 580W CPU) and I'm going to get a GTX 570 (not sure about the distributor).
Do you think a Gigabyte 580W PSU can support a GTX 570? My hardware guy is assuming yes, but when I used a PSU calculator it told me I needed at least 680W (even bigger than my last PSU). However when I Google people with similar rigs, many users are telling them that their 500W/450W PSUs are fine.
If it isn't enough, I'll just have call the guy and cancel the order, then built one myself (something I'm trying to avoid because I have no free time these days).
So around 350W if you can manage to make everything draw peak power at the same time, which hardly ever comes anywhere close to happening in real life. Unless you massively overclock and run FurMark, you would rarely break 300W.
I'm living overseas, so a lot of the brands and values people are recommending me either don't exist or are ridiculously expensive over here. The thing I took away from this is that I didn't need a huge number but rather a quality brand, so I decided to get a Corsair GX600 because it was the best bang for buck and I'm able to order it on the internet here (I can't use sites like NewEgg).
I learned that I shouldn't try to buy these kinds of PSUs in person because here in Korea, no one outside of hobbyists has even heard of a PSU above 500W and you can not buy one in a shop, unfortunately.