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.
A 6600GT is overkill even for 1.6....lets be honest here guys, nailing the 100fps mark in 1.6 isn't exactly difficult.
If you're looking to do it in source, It'd completely depend on the res/options/system specs you've got selected. So give us an idea as to what kind of system this card will be going in, if it's AGP or PCI-E, and what res/effect level you're looking to run it at.