I decided against it and am going to look for a lower cost player with stereo out. They are a bit hard to find however. The closest I can find is a bit over $300 and at that point, I was thinking the extra $200 might be worth it.
Regarding the HDMI passthrough, my understanding is that the HDMI input can be sent to the 2 HDMI outputs. In my setup, I have a flat screen in a room that also has a mounted projector. The Apple TV4 is going into a receiver and then by HDMI out to the projector. I use both screens and would prefer not to have to buy a second Apple TV4 or unplug cables. The receiver only has a single HDMI out.
Schoeps MK41 & MK4V | Schoeps CMC6, Schoeps KCY, AKI/2C, PFA, Nbox Cable/PFA | Grace V2, Nbox Platinum | SD744T, Sony PCM M10
Canon 16-35mm/2.8L mkii, 24-70mm/2.8L, 70-200mm/2.8L IS, 50mm/1.8 mkii, 135mm/2L, 100mm/2.8L IS, Sigma 35mm/1.4 A | Canon 6D, Canon 20D