S M P S

The reason for the extra 4 power connectors is to provide sufficient power to systems without overloading circuits. I have seen builders and even OEMs use 20 pin ATX connectors on a 24 pin board, but I don't recommend it.

I would upgrade your PSU before you add anything else to the system, especially a PCIe graphics card.

I recommend a minimum of 550W active PFC 80+ PSU. Here is a thread that is very informative. I suggest you choose a PSU from the brands and models that are listed there.

http://www.techsupportforum.com/forums/f210/power-supply-information-and-selection-192217.html

May I know what problem may arise after use of 20 pin ATX connectors on a 24 pin board ? S o that I will TRY TO avoid the couse till upgrade my PSU.
Thanks to Power Supply Information and Selection

The reason for adding the extra 4 pins to the ATX connector as well as the PCIe connectors and the CPU (4 or 8 pin) is to allow enough power to reach the components that need it safely.

Mainly, if your computer components aren't recieving the power they need to operate it can cause system instability and damage to components. I recently repaired a Acer for a co-worker that came with a 20 pin ATX connector to feed a quad core Athlon. He told me that, since the computer was new he would suffer frequent black screens and other stability problems and that the computer would just shut off for no reason. I replaced his PSU with a Seasonic unit with the proper connections and he has had no problems since.

Drawing too much power through the circuit (especially the high resistance areas like the connectors) can cause burnt traces, melting wires (which lead to shorts) and in rare instances, fire.

In my area COOLERMASTER & CORSAIR PSU available , so can you suggest me two to three model/ series PSU for above config.

Please chack following link and there is a diagram for exceed 4pin including 20pin . May I try once with FPS400-60THA-P for gaining my extra 4pin as diagram given.

Connecting 20-pin ATX PSU to 24-pin Motherboard, Adapter Info

You may do whatever you wish, it is your computer, but I cannot recommend anything but a proper PSU.

I suggest any of the Corsair TX series PSU's (or HX if you want the convenience of a modular design). This one would be perfect for you.

Newegg.com - CORSAIR Enthusiast Series TX650 V2 650W ATX12V v2.31/ EPS12V v2.92 80 PLUS BRONZE Certified Active PFC High Performance Power Supply

Get a good quality 650W PSU and it will have all the required connections and power.
Go with the Corsair.

The power supply is the most important part of a PC to me. A weak power supply can do all kind of weird things and problems and burn things up. And I don't think you can beat a Corsair.
Good Luck and God Bless Johnny

Thanks for all information.