Can a set of Ls50 metas surpass or equal a set of Kef blade metas with subwoofers

Don’t discount the driver differences. 

The blades crossover from the woofers at 300hz based on measurements. Kef claims 350hz.

the sub will be fine at 80hz and down but there will most likely a sound power issue between the 80hz and 300hz crossovers if you ran the SL50 with subs. The big heavy drivers of subs don’t play really nice above 100hz. I am sure there are a few out there though.

At low level there might not be too much difference if your not critical but push the sound pressure and integration issues and distortion/compression will surely show it’s head

Personally I don’t care for subs with small speakers and I think they blend a lot better for critical music listening with larger speakers. Think of it as turning your large 3 way into a very large 4 way.

Probable not surpass or even equal, but your setup looks like it would sound very good.  One of the big points about the Blades is the full range dispersion pattern which your setup lacks.

l researched the blades and stereophile said the UNI Q module was crossed over at 300 if l read correctly..

The blades crossover from the woofers at 300hz based on measurements. Kef claims 350hz.

Those are, I believe, all in reference to the original Blades and not to the newer Meta versions where the crossover has been raised to 450Hz, according to KEF.

I've tested my 8 inch subs...they will play upstairs in the 100 hz range quite nicely...lm very happy with the results..lm sure a set of blade metas and a six pack of Rel subs would do a better job...lm just so impressed what a 1500.00 dollar LS50 can do with subs..

I agree, based on my experience,  it’s objectively hard to beat ls50 meta and even a single well integrated quality sub for good sound at spl levels most people would typically want. It can be done but not easy especially for the cost.

Having said that, subjectively one never can be sure what will tickle another’s fancy best so that is a totally different story.