imo you should firstly get one 6950, it will always be better than 3x5770,
1. you have more memory
2. you can unlock it and gain performance boost
3. there are only few things that support CF, and less that support 3 way CF
if one 6950 won't be enough you can always get a second one or flash it into 6970
Why would they add something to a card that if you use it it voids warranty?!! Retartded in my opinion but I have recently found a 5970 for under $450 brand new so I will use that instead, then if I need to upgrade I will just Crossfire another 5970 with either a Silverstone Stryder, Thermaltake or Corsair 1200w PSU!