Long time lurker first time poster
I've been researching mining for a little while, so i'll give my opinion
If you want to know if your build is good for you and it really depends on what you want to use the computer for when you are not mining? I'm guessing you want to do some gaming and mine when your not using the computer for based on the crossfire.
If you wanted a dedicated mining rig i'd say your way off, what you need less processor more/better video cards (although 6970's are alright if you already owned them). If you just want to be a part time miner it can work you just need to check your numbers.
depending how much power costs wherever you live you may not making very much (btc earned - power cost). But if power is free for you; you could just go for it.
Some things to think about:
-If your rig is in a closed case make sure your case is well ventilated it will get hot in there heat = death for electronics
-it could be loud depending on video cards hopefully your computer is somewhere out of the way
-room could get warm, probably not too much with 2 cards but when they run 24/7 could be noticeable
-you'll wear out components faster
my 2 cents