Apparently the Onkyo TX-NR717, TX-NR818, TX-NR1010 and TX-NR5010 do support surround sound audio files. They don't support AC-3 (Dolby Digital) sound files though, but multichannel files in the WAV (PCM), FLAC and TrueHD formats should work.
Thank You! I think my friend has the TX-NR717. I will test this out immediately! Also, for some strange reason, I have made a DD-WAV file on my PC, but according to the file details (Win 7) it shows as being 2 channels.. Is this normal??!