To add to what chris661 has said, the LS50 Wireless are tuned to 43Hz in standard mode. You can choose less extension (46Hz) or more bass extension (40Hz). I’m sure this has been changed since launch as my review had the standard setting down as 45Hz. Looks like I’ll have to go back and update the review again!
Adding a sub to this - when set up correctly - shouldn’t sound like you have a sub connected. It should just sound like the KEFs reach deeper, the sub shouldn’t stand out in any way, so placement is important, as is choosing the right crossover point for the speaker and the room. As an example, I have a bass peak around 70Hz, so if I let speakers handle that range rather than a subwoofer, that frequency band isn’t as excited as it is when a more capable sub is covering that range.
You should end up with the LS50 Wireless (or any other speaker for that matter) sounding sweeter as a result, producing less distortion, and gaining more headroom as the speaker won’t have to do the low stuff. If adding a good subwoofer, I’d be inclined to set the LS50 Wireless bass to less extension - doing this will make sure that what they do cover are well within their capabilities, and you’ll be relying on less DSP processing too.
Also, having a sub in any system allows you to control the level of bass in relation to the speakers, so there should never be ‘too much’ or ‘too little’ - you can set it to however you want it.