I did when I got them. Of course, crossfire wasn't even supported when I bought the cards, had to wait a couple of months for the option to enable them. Even after that, there wasn't an improvement. Granted it has been a long time and crossfire is more mature. I was still thinking if the cpu was a bottleneck. If not then I can hold off for awhile, just had some cash burning a hole in my pocket. But, if it is better used for a complete future build, then I can wait.
I have the Cooler Master Stacker 830 SE with the 1000w psu, so power and cooling shouldn't be an issue with any upgrade. Not sure how good that psu is..but it has alot of connections.