Radeon 4870x2 vs firegl v8600

I am an architect and am building a new render system, I know that the firegl cards render quickly but they do cost huge amounts of money. I also do some casual gaming but not too much anymore. My question is a price based one, a good firegl card will cost at least 1000 for the type of renders that I do, and will have 1 gig of video mem, how would its render performance compare to 2 4870x2 in crossfire which have 4 gigs of memory and a faster speed while being cheaper? I suppose the comparable nvidia cards could apply to the question, quattro vs geforce