High value, giant killer speakers?

Usher DMD Mini Dancer 2 w/pr of Rel subs.
Avalon Eclipse w/Pr of Rel subs 

Vandersteens - all of them. I honestly prefer the 2s to the 3s, even though the 3s are more accurate, and the 2s with a pair of the subs over the 5s, for the same reason.

2s are a bargain classic, but I like the later larger models which have better tweeters as well as what is basically a subwoofer built in. My 4As have stood up very well and the 5s are just a refinement of them, in a sense, and should be available used now for a decent price (c. $7K)

Check out Seaton Sound and JTR Speakers.  Both offer extremely high performance speakers and subs at prices that are a tremendous value compared to many of the main-stream and boutique companies. 

Absolutely thrilled with the performance of my Tekton Double impact monitors, giant killers for sure

Absolutely without a doubt the new Sonus faber Sonetto 5's. I've owned Focals, B&W  702's and 705's (originals) and Sonus faber Venere 2.5's. For $4,999.00, these speakers far outperform their cost, and compare very favorably to others at twice the price or more. Designed and built in Italy with new woofer design and trickle-down tweeter design, the Sonetto's sing beautifully. Imaging, detail, separation, and easy placement are strong qualities. And their look speaks for itself.