Wouldnt 2 Ati HD 4870's be the same as a single 4870x2?

Im planning to get another 4870 1GB as my has worked so wonderfully with me im just just wondering if it will get the same fps/ performance as a 4870x2 or maybe even better?
ive got a 750 watt corsair PSU so i think i can support it. Anyone think that its worth it? Oh and also does Crossfire improve media encoding at all? just wondering since in the future i plan to be a motion graphics designer

here are some links for you to look at and judge for yourself -
Two 4870's VS One 4870x2 DOG FIGHT!! - Overclockers Forums
AnandTech - New Build, 4870x2 or 2x4870?
Would cf 2x4870 & 4870x2 be the exact same? do they all use gddr5?
PSU for 4870X2 - EXTREME Overclocking Forums
2-4870's or a 4870x2? - techPowerUp! Forums

sandra lite 2009.5.15.99

i have 2 512mb 4870s CF.

my opinion would be that two 1gb 4872s CF would be equal to one x2. i don't have 30" monitors either--just two 19". so my CF setup suits me very well for what games i play.