Re: What is your opinion on CrossFireX and SLI?
The problem with SLi or with CrossfireX is that you don't double the performance with two cards, or triple the performance with three. I may be incorrect, and anyone correct me if I am wrong, but it is my understanding that every card you add "helps you out" less and less.
The decision comes down to personal choice, if you have the money, and one 480 or 5970 is not enough, the only way to increase performance is add another one.
Would I personally add a second card for a performance gain of less than %100, no. I am very pleased with what I have now.