I don't know how many % of things the guy on OC.net is right but his part about nvidia cards consume more power to gain 1.1 support is completely wrong. Nvidia gtx600 cards need more power because nvidia pre-OCed them to fight against AMD cards ( with low stock clock ). If nvidia doesn't feel like pushing high core clock on a model then it will be very efficient in performance/watt ratio, for example the gtx650ti. Plus if you read the replies below:
"This week I installed an Afox HD7850 2Gb low profile card in an Acer Veriton S661 that has the Q35 chipset, PCI-e 1.1 x16.
Card works like a dream...."
"I have to disagree slightly with this article about the Radeon HD 7770, I to had the same fear but after doing some research decided to just recently pull the trigger, I purchased a gigabyte factory OC'd HD 7770 1GB card for my older LG775 based system with PCI 1.1, I was replacing a Geforce 8600GT. After removing the 8600 drivers completely I shut down and installed the 7770, system booted fine. I installed the latest catalyst drivers and everything works great."
Conclusion : nvidia fanboy failed to make a statement against AMD. If you still want to be sure then contact gigabyte's support service, remember to provide detailed info.