Hello,
You can do optical, but you won't get uncompressed 5.1 sound, meaning no Dolby True HD, and no DTS HD Master Audio. As for video... well, you won't do HD content justice. I recommend investing in a more up to date receiver. You could do HDMI to TV those that can, and optical to receiver to surround. Though Dolby True HD and Dolby Digital are night and day.
All the best!