Power Supply Advice Required Please

[GarryJames]

I have decided to upgrade my graphics card to a EVGA SC Nvidia 680 GTX, however I realise due to the OC that the power specs are different and the Nvidia spec sheets says it needs a 550 watt power supply with a 38 amp on the +12 volt rail. ( this was for a system fitted with an i7 intel 3.2 GHz processor.

http://www.evga.com/products/pdf/02G-P4-2683.pdf

I bought my PC from PC Specialist and I understand that the system is fitted with a power supply that has the following

Manufacturer - FSP
Model - FSP800-80GLN(85)

DC Output
+3.3v 30A+5v 30A
+12V1 20A
+12V2 20A
+12V3 20A
+12V4 20A
+5Vsb 3.0A
-12V 1A
Total Continuous output 800W

1x 24pin ATX (20+4)
1x 8pin CPU 12v (2x4)
2x 6pin PCIe
2x 8pin PCIe (6+2)
2xSATA (1x3, 1x2)
2xMolex (2x2+2floppy)

Am I correct and reading that the +12v rail only has 20 amp and will I also need to upgrade my power supply too?

I took it for granted as this power supply runs my current rig and my son's who has a Radeon HD 5970, I assume this would require more power.

Can anyone confirm for me please?

Many thanks

 

[GarryJames]

Just to avoid confusion as I cannot edit this - my son's system has an identical power supply, I don't run two computers off of the same one