I have both ls50s and ls50 metas + sub and have auditioned those larger newer KEF models as well.
The original ls50s are very good but the KEF product line overall has improved significantly since the original ls50s. That applies to all current models from ls50 to Blade.
The ls50s are the bees knees for their size IMHO and many agree based on feedback and reviews. THeir limitation is how loud they can go without distortion in that KEF squeezes a lot of quality sound out of a small package but it is still small and best suited alone for smaller rooms. Use of a subwoofer can up the game to compete well with larger more expensive models, especially if an active crossover is used to offload bass from the little ls50s.
So yours is a very common scenario. IF you like the sound but just need more, then moving up the line in the R series is the way to go. THen the ref series is a yet cut above the R series in general in regards to overall build quality and performance. Most people will have no need to go there but teh boiled in the blood hardcore audiophile with a proper budget still might. Then there is the Blades which is the ultimate if one has teh proper space and budget.
But the good news is even little ls50 metas + sub set up well can get you practically all of what you might get otherwise, at least in most people’s modest sized rooms at home, as long as the are able to go loud enough to fit the bill. Room acoustics are likely to be the only remaining significant challenge perhaps in many cases.
THen you have the ls60s which is also likely an end game setup for many especially those who value space and convenience.
All good stuff. Choose wisely and enjoy.