dissapointed - new LS50w's vs old PioneerFS52's/Luxman R113 - so far Kef's not so great?

I own the LS50s (passives), feed them with 60w per channel and mate them with a sub in a room that is too big for them alone w/out a sub.
It took about two-three weeks for me to break-in the speakers. But they never sounded harsh, boxy or unrefined in any way during the break-in process.
After the break-in, I noticed they opened-up significantly, the sound became more transparent and I could more easily discern the quality of the records. A change in amp is very detectable on these speakers.
Overall, they are very neutral, honest and smooth speakers.
Before these speaker I was a non-believer in break-in, but these are really such speakers that the transformation is very noticeable.
Then I wanted to go u/g to the LS50w. I heard them on High-end audio in Munich, they sounded very nice with vocals, but I noticed the boxyness.
Second time I heard a pair right out of the box with zero break-in and they sounded very muffled and boxy. I decided not to upgrade.

P.S. An advice:
Let them break-in and don't do the A/B comparison all the time. Play various genres of music for about a week, then you will be able to build your opinion and possibly appreciation of the speakers.

Then play your old setup for a day or two and you will notice either why they are better overall or notice their drawbacks against a more neutral and honest speaker. A flat response speaker will always lose in A/B comparison to a one that is colored to excite on first hear, just like those TV sets in a store with maxed contrast and backlight. Bring it home with those settings and you will get blind.

I've owned KEF LS50s for several years and found that they are quite sensitive to the equipment they're partnered with. Impedance drops below 4 ohms at low frequencies and you need an amp with good current capability to hear them at their best. If you have room problems (wall reflections, etc.), you will definitely hear them with the LS50s, but that's true of most highly-resolving speakers. As with most small standmount speakers, a good subwoofer is required for bass response below 50Hz.

For me, they offer a musical experience that is unmatched at their price point. 

I think people read the class a rating of the speakers and expect more than a single 51/2" woofer in a small box is going to be able to deliver. Toe in with uniq drivers is also critical with regard to distance from side walls and room treatments.  

LS50's are the poster child for why one should never believe "professional" reviews.