Newbie question regarding DAC...

I should list my equipment first to get a more accurate answer:
1. Pair of Klipsch RF6 Reference speakers.
2. Pair of Definitive Technology Studio Monitor 65's.
3. One Definitive Technology Pro 2000 center speaker.
4. One Power Sound Audio down firing sealed Subwoofer with built in 750w RMS Amp.
5. One Emotiva XPA5 integrated Amp.
6. One Yamaha RX-V863 Receiver with full set of Pre-outs (Not using this Receivers Amp, just my nice quality RCA jacks to the Emotiva Amp.)
7. An Oppo BDP 103 CD - Biuray player for sound source.

I'm using a Dolby Optical line from the Oppo unit to my Yamaha. Out from the Yamaha's pre-outs to the Emotiva XPA-5 RCA inputs.

I keep my Yammy set to it's 7 channel stereo setting. This is because all my speakers are spaced apart in a forward facing position because I don't use movie surround. This positioning and setting sounds best with my CD and Pandora for music only.

Given this set up and configuration am I not realizing an all analog signal or is my Yammy converting that optical sound source from my Oppo 103 to Analog? If not, would it be wise to add a DAC unit so that I could go out of my Oppo player to a DAC using Optical input from Oppo to the DAC, then optical out from the DAC which would convert the Multichannel digital signal to pure Analog to my Yammy receiver, thus giving me Analog signal out of Yammy receiver to my Amp and all my speakers?

I can not go out of my Oppo 103 with all separate RCA because it does not provide enough RCA outputs to plug in my Yamaha receiver in order to run Analog to all my speakers. Hence my utilization of the Dolby Digital line.

Best I can explain it... So question is will a DAC do this Analog conversion task in Stereo mode to my Yamaha to provide all Analog output to my Amp?