Where says a 430W will be ok? I checked both Nvidia's website and a PSU calculator.
Nvidia's GTX670 spec's http://www.geforce.com/hardware/desktop-gpus/gefor
"Minimum System Power Requirement (W): 500W"
http://www.extreme.outervision.com/PSUEngine with 30% capacitor aging also suggests a min 499W needed
both say 500W min (for a single 670), so personally would go for a little more (just to be safe, for the future) if I was to build a pc today. Probably look at 750-800W if I was going to think about SLI GTX670
Please mark this response as "Accept as Solution" if it answers your question...
but please understand that the solution may not be the answer you're wanting to hear...
If you have found any post to be helpful, even if it's not a direct solution, then please provide that author kudos - spread that love
Lithium - helping nntp users with mania, depression and headaches
They suggest 500W because of crappy PSUs that can't provide their nominal value. A 430-450W brand PSU with 80%+ efficiency is enough. I have a GTX 560 Ti based rig at home (with i5-2500K), its suggested PSU 500W, too. I run my system with a Corsair VX450.
VGA manufacturers just wants their arse protected, that's why they suggest way over its real power consumption. That's what a calculator does, too. But they can only confuse those who don't familiar with electricity.
But all you should do is adding CPU's and VGA's TDP. For example: a GTX 670's max TDP is 170W. i7-2600K's max TDP is 95W. It equals 265W (max!). And no, the rest of the system doesn't consume - almost - another 265W.
Software: Inventor Series 2011 SP1 x64
OS: Vista Business x64
RAM: 2*2Gb GeIL
VGA: Quadro FX 550