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.
Go with the Leadtek or eVGA. Both look to be a good choice. I second the notion of kicking it up one more notch for a 6800NU (That's the base 6800, no letters or words after it. NU stands for Non-Ultra) which you can probably get for $250 or so if you look around. But if the 6600GT is pushing your budget limits, splurge on that and you should be happy. From what I've read, the 6600GT takes anything from last year's card series (9xxx from ATI, and 5xxx from NV) to the house Just make sure you get AGP if you have an AGP board (assuming you do).