QUOTE(kuanzc @ Mar 12 2011, 01:33 PM)
Could Silver Stone SST-ST400 support HD5750?
Yes, it will be able to.
QUOTE(Searingmage @ Mar 12 2011, 02:33 PM)
Just wondering, how do we know if a PSU is true power PSU or not?
Seasonice silence pro series are true power psu?
Also, Gold, Silver and Bronze, is there really a difference for PSU?
You can determine whether a power supply is a true power power supply or not by checking its 12V rail.
An example of a non-true power power supply :

This is the label of the Cooler Master eXtreme Power Plus 500W power supply.
Notice that the 12V rail's combined Ampere is 36A, but the output wattage is only 360W. If you try calculating its total wattage by using the formula ( 12V x 18A )², you're supposed to get 432W. However, the label states that it outputs only 360W.
To find out true ( A ) that this power supply has on its 12V rails, you can do so by taking 360W and dividing it by 12V, and you'll get yourself 30A, which is the true (A) that the power supply can output. 36A would be its peak wattage then.
An example of a true power power supply :

This is the label of the Cooler Master Silent Pro M 600W power supply.
It has a single 12V rail, and that the 12V rail can output a total of 40A. Now to find out if it's true, you perform the same calculation above, by taking 480W and dividing it by 12V. It gets you 40A

.
For the "Gold, Silver and Bronze thing", it's there to indicate how efficient the power supply is. The best rating would be Platinum, next would be gold, then Silver then Bronze. The higher it is, the more efficient the power supply is.