Question on GPU's

[AMDave]

GPU output should be the same.
Power cost should be lower overall with crossfire as you only use 1 mobo, HDD, PSU etc.
but you'd need a PSU that will handle the load of both cards on top of the rest of the load

edit - some mobos will run 1 GPU at x16, but when 2 are present, run them at x8.
if you can get a mobo that will run 2 at x16 it makes a small difference
but on second thoughts, you can run 2 gpus without them being in crossfire
best results in crossfire if both cards are the same, otherwise slows to rate of slowest gpu
so that can make a difference if both cards are not the same model