I don't really recommend micro-ATX for Crossfire as you limit the SPACE between the graphics cards for air flow.
Also, I'm not sure why you are switching MOTHERBOARDS either, but you may have to buy a new copy of Windows and reinstall everything which will cost you another $100.
However, you asked. I can't recommend a micro-ATX motherboard since you didn't specify the CPU. As for a CASE.http://www.ncix.com/products/?sku=84140&vpn=NSE-200-KKN1&manufacture=COOLERMASTER
That's a Canadian link.
Points:
1. Supports front USB3 (make sure motherboard has USB3 front output)
2. Organized to support long video cards (see pictures)
3. Comes with two fans (probably top-rear, and front-bottom)
4. Cable management.
If you get an ATX or other micro-ATX I recommend using the above points.
*Micro-ATX motherboards have FOUR PCIe slots available. That means two, two-slot graphics cards are very close together so the TOP card will get hotter than the bottom card. Again, I don't recommend this. I recommend an ATX case and motherboard.