Bill, your Epson front projector has only one HDMI input!
Ok then:
1. Connect the Oppo's (105 or 103) HDMI 1 Out to your Arcam HDMI In 1.
2. Connect the Arcam's HDMI Out to your Epson's HDMI In.
3. Select
LPCM for the HDMI Audio (from your Oppo's
Audio Format Setup menu).
4. Select
1080p for the Ouput Resolution (from your Oppo's
Video Setup menu).
5. That's it!
* For more advanced settings (audio & video), in your particular case, using your Epson 1080p front projector, your Arcam AVR350 receiver (with two HDMI inputs, version 1.1), and your future new Oppo Blu-ray player (in your particular case I recommend the 103, because the 105's main adventage is its advanced analog section, and its DAC section; which you may benefit, or not, depending of your setup), I'm always right here.
Bill, your Epson projector; which model is it? ...The PowerLite Pro Cinema 1080p UB, or the Powerlite HomeCinema 1080p UB, or another model?
P.S. Sorry for the delay but my computer was shut down for some 'security' repairs/maintenance.