Hi @Clementfufu 

Welcome to the Sonos Community!

I cannot recommend this set up as surround speakers are best kept at head height (of someone sitting down), which in-ceiling speakers obviously are not. In addition, you are paying more for less. It would be the cleanest setup in regards to wires, however.

I presume you mean near the ceiling? You can mount the Era 300s inverted. This setup will have the advantage of Atmos audio over the Amp configuration, but it is recommended to keep Era 300s at head height too, and the inverted mounting will affect the effectiveness of Atmos playback. You will need to provide power to the speakers, however, which likely means visible cables. One option is to install power sockets very close to the speakers - you may even be able to do this for around the difference in price between the 300s and the Amp plus speakers. Another option (but visually less attractive) would be the use of cable conduits.

It should be noted that TruePlay isn’t yet supported for inverted Era 300s, and we don’t yet have short power cables for Era speakers available.

Normal (not inverted) mounting of Era 300s at a lower height than your Ones are at now would be ideal, but of the two configurations that you specified, the Era 300 option would be best.

I hope this helps - if you have further questions please don’t hesitate.

In that setup, I would probably keep the surround speakers and get a speaker stand for the right side (facing TV) to hide the power cord.  You could lower the shelf on the left and shrink it’s size, or just get a wall mount to hide the power cord. I’m not sure how much room you have in that corner, but I bet you could get it so that no one is hitthing their head on it.  Or you could just get a pair of wall mounts for both sides.  If you’re still concerned that power cords are still visible, then you could get an in wall cable kit or just hire an electrician to put in power outlets exactly where you need them on the wall.

All of these options should be cheaper with better results than getting an amp, pair of in-ceiling speakers, and wiring the the speakers.