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

Unless the 'W' above is a mistake, the OP has the wireless version of the LS50's with built-in amplification, so I don't think the problem is lack of power. 

Personally, I lived with the original, passive LS50's for a year or so, upgraded virtually everything else in my system and added quite a bit of sound absorption to my room, but could never get rid of an edginess that was ultimately unacceptable to me.  Traded them in for more mellifluous speakers (Alta Audio Rhea's) and all was well.  They really should have decent bass, though, down to 40 Hz or so.  I suppose it depends on what level of low bass is necessary for your tastes. 

Some folks really do love them, though. Like John Darko:
https://darko.audio/2016/12/kef-ls50-wireless-review-dars-product-of-the-year-2016/
Have you tried the room correction/DSP?

+1 twoleftears   I really don't get this speaker and I've owned KEFs in the past.  They sound like they are out of phase to me and I've heard them with real power in a decent room.  Not familiar with the W ones.

The ls50s do what they do very well (very lifelike detail and coherency) but are small and thereby necessarily limited. Not designed for larger rooms. Yes they also require some muscle to be driven well. They will not shine otherwise and will likely sound downright underwhelming in larger rooms. Even in a smaller room a sub is needed for bass extension. I suspect many have bought these based on the deserved rave reviews and but with unrealistic expectations.

Have not heard those Pioneers but they are larger and likely not as challenging to drive so would not surprise me if they perform well with lesser amps but I would expect a much different sound that some might prefer especially in a larger room.

Apples and oranges are hard to compare.

may be GIGO.... you didn’t name your source solution. I ran the wired version of the LS50’s and found them quite resolving but if your source detail is mediocre you wont hear what you paid for. They are picky about room placement for bass because they are a ported speaker and won't please a bass head because the driver is too small for bass drum and fender guitar bass playback

No speaker sound ok in a room without room correction. Certainly not if they are standing on a desk and you are sitting close. You will experience this if you put e.g. a Martinlogan Unison in your source chain (ARC room correction - probably the best for small money). The LS50W will shine then. They do need separate subs though. They have nothing of interest to show you below 100Hz. I’m saying this out of experience. Actually I had them sound so good that I’m looking at adding a Ref 3 or Ref 5 to the collection. Very natural. My reference is the ATC 150 ASL