I thought using a 650 watt PSU was walking a fine line also, regardless of how good the PSU is.
That is why I put a 850 watt PSU in my 2600k SLI 560ti build. I did not want to have my PSU running at over 80% capacity every time I gamed. I wanted plenty of overhead since I knew I would be OCing and the price was good for a Corsair 850TX with 72 amps on the 12v rail if I recall correctly, along with 4 8pin PCI-E power connectors. I know it is not a modular PSU, but it is a decent PSU that has excellent reviews at the time of purchase. Plus my HAF922 case had plenty of room to hide/keep cables out of the way.
This is why I originally recommended he use his CX430 PSU to power the video card alone. Since it has a 8 pin PCI-e connector and a 6pin adapter could have been used for the 6 pin power connector since it has 32 amps on the 12v rail. Just to make sure it was not a lack of power problem.