yes its crossfire supported...just type in google 4770 crossfire and results will show that its a great crossfire setup
and yes it should come with a crossfire bridge
Uber
Check though because I bought one of my cards from sapphire and there wasn't a bridge in it, so I had to buy another for £10. My XFX 4770 DID come with one, so moral of the story..check the box. They are great in CF so worth it!
AC