Are you taking into account different uncompressed sound tracks in that calculation? I'm not saying it's impossible, just asking.
The audio for an acceptable quality 25Mbps for MPEG-2 should be less than 1Mbps, that is, it has to be compressed. If you need to use uncompressed surround audio, it would take a lot more bitrates (48kHz 16 bits 5.1 surround takes about 4.6Mbps, for one audio track).