Hi Andrew
My HiFi doesn't have Optical either. What I did (which works very well) is to purchase an inexpensive external DAC like
this (although some on this Forum have purchased more up market versions). Note, the DAC does provide you with RCA sockets.
You also need a special optical cable like
this, (which I think you can get from Brennan too).
I found that this was MUCH better than using the Aux out method to drive my HiFi.
Fred