I want to use my wireless KEF LS 50 W II's as my front L/R speakers .....

Hello paul2004,

Welcome to Apple Support Communities!

If we understand your post correctly, you want to know how you can use your HomePods as a rear left and right channels for Atmos. We're happy to help!

"Use HomePod with Apple TV 4K

If you have an Apple TV 4K and HomePod you can create a captivating home theater experience with a single HomePod or a stereo pair. When you set up home theater with HomePod, you can enjoy Dolby Atmos, Dolby Digital 7.1, or Dolby Digital 5.1 surround sound. (HomePod mini does not support Dolby audio formats.)

Note: Home theater requires Apple TV 4K with tvOS 14.2 or later. For more information about setting up Apple TV, see the Apple TV User Guide.

To set up home theater, you need an iPhone or iPod touch with iOS 14.2 or later, or an iPad with iPadOS 14.2 or later. Make sure that Apple TV is assigned to the same room as HomePod in the Home app.

Alternatively, you can set up the home theater on your Apple TV 4K with tvOS 14.2 or later (for details, see the Apple TV User Guide.)

1. In the Home app on your iOS or iPadOS device, touch and hold Apple TV.
2. Scroll down, then tap .
3. Tap Default Audio Output, then tap the room with your HomePod or HomePod stereo pair.
4. Note: This setting routes all sound, including navigation clicks, from Apple TV to your HomePod.

When setting up HomePod for the best surround sound, place the speaker within 10 inches (25 centimeters) of a wall and as close to the center of your TV as possible. If you use a HomePod stereo pair, place the speakers on either side of the TV. For optimal surround sound, the HomePod speakers should be about 4 feet (1.2 meters) apart from each other."

Use HomePod with Apple TV 4K

Let us know if you have any questions.

Thank you for using Apple Support Communities.

Take care!

Thanks for getting back to us, paul2004.

Per the article, Play audio in Dolby Atmos or surround sound on your Apple TV - Apple Support This is what is supported with Apple TV:

Setups you can use

On Apple TV 4K with the latest version of tvOS, you can listen to music, movies, and TV shows in Dolby Atmos. You can use the following setups to play sound in Dolby Atmos or surround sound:

• One or two HomePod speakers*

• A television that supports Dolby Atmos audio

• A Dolby Atmos compatible sound bar with a television that supports Dolby Atmos audio

• A Dolby Atmos-enabled AV receiver

* Your Apple TV and HomePod speakers automatically play sound in Dolby Atmos or surround sound if it's available with content that you watch. HomePod mini doesn't support Dolby Atmos. If you want to set up home theater audio with HomePod, find out how.

If you're looking to set up multiple speakers for surround sound, you may need additional equipment to support it. Should you need further help, contact Apple Support:

Contact - Official Apple Support

Cheers!