Hello Neil. Welcome to AOS.
Hi End or Low End, it doesn't matter, our members like and use all types of equipment. Vintage gear is very popular.
The LS3/5a speakers in your link are not three way, they use two drive units and are a highly respected vintage classic design. But tend to be very overpriced these days, with some variants fetching around £2000 a pair. The quoted £680 is probably reasonable given going rates, but I'd be surprised if you found them a huge improvement over your Charios.
If you have ideas that you'd like to discuss. Start a thread in the Blank Canvas area and outline what you have in mind. I'm sure you'll get plenty of replies.
You'll find plenty to interest you here.
Enjoy the forum,
Geoff.
It is impossible for anything digital to sound analogue, because it isn't analogue!