I plan on upgrading my computer by the end of this year. I am moving from an ancient AMD 3000+ with ATI X300. I am confused as to whether or not I should get SLI GTX 280's or Crossfire 4870 X2's??? I am confused because, even with all the hype that the X2 had, since it came out, I have been reading some threads, and some say that the GTX 280's are better???