Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.
Any 4x or higher AGP card can run at 1.5V. I believe some 2x cards could too, but most were 3.3V. So just don't stuff a 2x AGP card in a mobo that doesn't support 3.3V. If I remember right *most* 4x mobos will handle a 3.3V card, but not all, so check. 8x AGP mobos generally only work with 4x and 8x AGP cards.
At any rate, you'll be fine unless your mobo is really old. I have no clue if a GF 6xxx can run on a 1x or 2x board (but why the #&*%^$&^! would you want to?)
You know, it would have made a hell of a lot of sense if they'd keyed the AGP slots for voltage like they do with PCI...