How do the Elac Uni-Fi UB5s compare to more expensive bookshelf speakers?

I believe in your premise Kalali, balance in a system is important, otherwise one is always chasing the 'weak link'. I have no doubt that the LS50 is capable of exposing the differences between a $500 SS amp vs. a $2000 tube one. Likely the UB5 could do the same. However pairing a set of speakers with an amplification costing 5-10 X the cost is not advisable (not saying you implied this). That said, I can't say I agree when I hear one advise others that they should spend 1/2 their audio budget on speakers. There are situations (upper end budgets) when this may be justified however not for the majority. 

 

I understand your desire to change the sonic character of your system via speaker change. Serves as one of best ways to explore and discover which sonic characteristics are most important to oneself. After that one can then improve on the quality of the desired presentation with the purchase of a more refined speaker having the desired characters. From reviews do you get the impression that the Elacs are brighter than the Wharfes? If so maybe you should give them a shot.  

With your amplifier you are positioned for speakers that are more refined than the Wharfdales or Elacs. Of the speakers you mentioned, I have heard and really like the Dynaudio X14s. They sometimes come up used here on AG. I intend to purchase a pair myself when a pair comes up at my price.