Well, at first only the Sapphire X800GTO2s, priced at around 180-190, were reported to being able to unlock another 4 pipes (They OC'd extremely well too). The card got popular and become OOS. So newegg decides to jack the prices up to $280. Then people began getting similar results with the Connect3D X800GTOs, so that became hot. I guess after a while, the supply of 480 cores ran out (I forget the other one). The Connect3D X800GTOs were no longer unlockable. Then PowerColor releases their 16 pipe X800GTO. It doesn't OC as well as the X800GTO2, but it's cheaper and you don't have to go through the hassle of unlocking the extra 4 pipes. If you don't plan on OCing, I highly suggest getting the PowerColor X800GTO@16 pipes. If you do plan on OCing, the Sapphire X800GTO2 is the card to get.
EDIT:
I just took at the benches posted by Wreckage. Apparently, the 6800GS is killing the X800GTO (although they are only at 12 pipes). It's practically dead even with the X800XL (which is essentially the 16 pipe powercolor), which is strange because the 6800GS only has 12 pipes. So I guess the choice now is between the Sapphire GTO2 or a 6800GS.