Hi @voknil, thank you for reaching out to us, and welcome to the Sonos community. I appreciate you for bringing this concern to us. Let me help you out with this.

Placing your Sonos speakers to the right location can achieve its best sound and wireless connection. The Arc has two up-firing speakers within it that sound best when positioned either on a tabletop, or wall-mounted below a TV. Also, Arc requires a minimum of 5.5 inches on the front and sides of it, with at least 2 inches between the backside of Arc and the TV when in a tabletop orientation. If wall-mounting, it is recommended to have a clearance of at least 5.5 inches between the TV and Arc. Your rear speakers or surround on the ear level and should be at least 2-3 feet away from the nearest wall.

Arc smartly detects when it is attached to the mount and automatically adjusts the EQ to temper bass resonance from the wall. You can adjust the bass, treble, balance, or loudness of your Sonos speakers can be done in a few simple steps using the Sonos app depending on your preferred sound.

You can tune your Sonos speakers with Trueplay. Trueplay measures how sound reflects off walls, furnishings, and other surfaces in a room, then fine-tunes your Sonos speaker to make sure it sounds great no matter where you've placed it.

We can wait for suggestions and feedback from our Sonos community members, they might provide a suggestion about this. You may also contact our Sales specialist for more information.

If you need help with any other information, please be sure to let us know. The Sonos Community is always here to help.

Placing the Arc behind the TV would severely compromise the sound quality and surround effects IMO.  I have never tried it..   .but there is a reason for that.

I realise that there are design and aesthetic reasons for putting a TV above a fireplace, but this usually results in the TV being placed too high for optimal viewing.  

… not to mention the cumulative effect of heat and dust wafting up from the stove beneath.

Thank you for the help and guidance. As it is a pellet stove insert the dust will be contained within the unit. And the heat is distributed via fan and blower so should direct out and away from the TV. Plus a large 8” deep barn beam mantle. 
 

My main concern Is the space. I don’t consider myself an audio purist so trying to get a sense if this setup would sound good still acknowledging it is not the optimal setup. Or would this be a total waste of money. 
thanks again so much for the expert advice!