After building a computer up from scratch save for some ddr3 memory and the power supply, i discovered that my motherboard has two 8-pin ATX 12V (PW12-1 & PW12-2) power connections, for which i have only 1 cord for. Assuming that my power supply is inadequate as the computer flickers to life for approximately a millisecond before going silent, i am in the market for a new one. However i have limited experience in buying supply's and would value some input upon recommendations for my system.
I Would like to thank the both of you for your fast and valuable input. however i have concerns about the hcg 620, its connecters are listed as 1 x 4+4 and 2 x 6+2's it makes me feel like i would be able to power my motherboard but my graphics card which has 2 x 6 slots for its power would have to suffer sharply in performance or be underpowered, are my concerns unfounded?
For a system using a single GeForce GTX 560 graphics card NVIDIA specifies a minimum of a 450 Watt or greater power supply that has a combined +12 Volt continuous current rating of 24 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors.
Total Power Supply Wattage is NOT a crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important.
Even the Antec EarthWatts Platinum Series 450W (EA-450 Platinum), with its combined +12 Volt continuous current rating of 34 Amps and with its two (6+2)-pin PCI Express supplementary power connectors, is more than sufficient to power your system with a single GeForce GTX 560.
A single (4+4)-Pin ATX/EPS connector connected to the motherboard is more than sufficient for the Core i7-2600 CPU that you are using.
The 4+4 and 6+2 connectors are to improve compatibility. The 4+4 works with 4 pin and 8 pin CPU power connectors, the 6+2 pin PCI-e connectors work as 6 pin connectors or as 8 pin connectors, in your case you would just leave the two extra pins on each one hanging off when you hook the 6+2's into the 6 pin slots on the GPU so it won't be underpowered, it will be power appropriately.