Even if present in testing (and unstable too), the current xserver-xorg-video-intel package version is quite outdated. You should compile the one in experimental to support the latest hardware. Here you can find the i386 and amd64 packages (and sources and compile logs) for wheezy: https://drive.google.com/folderview?id=0B7AdLMiZn4Fzdm9LTVFlWG5XcWs