...sorry but WGH is wrong. You can use that player as an analog surround preamp which means that you can use that emotiva amp for a 3.0 system.
I didn't say it wouldn't work, I said it would sound like crap compared to a good quality AV receiver. And the Emotiva will only power the speakers when playing a disk. The Emotiva is really the wrong tool for a job. Does your Mom dream of owning a mini home theater with all it's speakers, electronic boxes, complexity and wires? Or will a soundbar placed under the TV work just as well? Or do you live with Mom and this is really for you?
The Oppo 103 DOES NOT have any audio inputs (RCA, HDMI or Optical) so the Oppo cannot be uses as a control center. The speakers will only work when playing a disk, NOT when watching broadcast, cable, or streaming TV. The Oppo does have a menu with 12 selections to select for internet streaming. I have never used it, the selections may work for your Mom but I doubt it.
When your Mom watches a blockbuster movie on Amazon the sound will come out of the TV speakers instead of the GR Research speakers because the TV cannot move the sound into the Oppo/Emotiva combo. If your Mom only watches movies, the Emotiva will work just fine but if she is like me and watches TV and streaming shows too then the expensive LGK 2.2 and Emotiva combo will not be used 99% of the time.
When my Outlaw processor died I researched and read a lot of reviews before replacing it. The only product that got zero negative reviews were made by Anthem. I wasn't planning on spending that much but I did and happy I did. I read reviews on any product before buying, if it has 50% good and 50% bad reviews I pass. All the receivers and processors I looked at were 50/50 except Anthem (which is above almost everyone's budget).
Emotiva sells the BasX A3+ as the "Perfect upgrade for the front three channels of your AVR." First you will need a low powered AVR with line out (not all AVR's have line outs) and then add the BasX A3+ to add more power.
https://emotiva.com/products/basx-a3-plus-three-channel-power-amplifier