Required strength for GTX 260+ OC

Hi!
In general I even would say that a 400W is enough to run your system.
But what other components?
It is a difference betwenn an i7@4.0 GHz and an Intel Core 2 Duo @ 3.3 GHz.
For efficiency, temperature and noise level, I would recommend a 500-550W PSU when you run a powerful CPU besides.
For a CPU with a TDP of 95W or lower and no overclocking, you can choose a 400W PSU.

@dunde
If you have one or several rails, makes really no difference in what the PSU can do on 12V.
Here are two other threads about this topic, please have a look in it.

Because the 12V line is coming from one transformator, if you have one or 4 lines....makes no difference. One line is 32A, two lines have as combined power 32A. No difference at all. All other things about this topic I wrote in the other threads.

A good 400W is really enough if you don´t want to extend the system later with a DUAL-GPU card or SLI/CrossFire.

I have HX520 and it runs fine