Considering he says that NVIDIA said their 6xx cards use more power than the AMD 7xxx cards, which is not true, and NVIDIA would never say, and that he tested low end NVIDIA 6xx cards that are just rebadged 5xx cards I would tend not to believe him. And of course sapphire is going to say the cards not fully compatible with pcie 1 as it doesn't have enough bandwidth.
That being said, you can't get a pcie 1.0 card anymore, but spending money on a high end card new card you can't really run is silly too. Just get a 6670
I should add that chart to my signature, given how often this question comes up. Seems like I see it three times a day, and I spend less than an hour a day on this site.
Also, I was under the impression that only some 2.1 cards had issues in 1.0 boards, and only those that were pushing the power limits of the 2.1 slot? Never actually seen anyone have a compatibility problem, though.
I've seen a few times 2.1 card gets recommended for 1.0 user slots and then two weeks later he asks for help troubleshooting. In the end, it would appear that the card works in another PC but doesn't in his, and the power supply unit is adequate. I've seen it 3 or 4 times since last year.