High value, giant killer speakers?

Magnepan are my absolute favorite for the money.  I just upgraded from 1.7i to 3.7i and couldn’t be happier! The sound is really hard to believe. Unfortunately, unless you have a truly powerful good quality amp, you will be very disappointed.  My best friend just received his new LRS Magnepans but is running them with a NAD M32 and the amp just won’t power them.

I don't think Maggies need a high-wattage amp so much as they need an amp with a very robust power supply. I had no problem running Maggies with a 90 watt/ch amp with 72,000 microfarads capacitance and huge EI Core transformer. 

The problem with the NAD M32 is its class D topology - a topology which always sounds weaker than the specs suggest. It's why it takes a 1000 watt class D sub to match the grunt of a 500 watt AB sub. I don't know the teachnical reasons for this phenomenon, but IME, class D always sounds/feels about 50% the strength of A or A/B amps.

Back on topic, I find the Maggie .7s are the greatest value of the brand - even preferable to the 1.7i.  I much prefer Spatial Audio's open-baffles to the 1.7s, but compared to the .7s, it's a tougher call. 

   Did that twice accompanied by great dissatisfaction once in the home. Not very well schooled on the giant killer thing. The venerable speaker system that I wanted was and still is fairly priced which is subjectively expensive. 
   As luck would have it an original owner pair popped up on the local Craig's List in Portola Valley priced to sell quickly by a very well healed young stock optioned millennial noid with a new baby. His cup runneth over right into my Land Cruiser. 

Save up, get what you want used and stay off that merry-go-round. 
   
 

Emerald Physics have won numerous awards and are very reasonably priced

Another vote for Magnepan LRS.
Right room / Right electronics = true high end sound / experience.

Speaker preference is so extremely subjective that any particular choice, even ultra-expensive models, might be horrible sounding to certain listeners.  Therefore, any "giant killer" candidate must be auditioned by the buyer before being considered.  I fear that these types of inquiries are a search for a rough consensus that is then used to make a choice without actually audition.

The mention of Magnepan speakers is good because one can easily find them for an audition.  I would add lower end Audio Note speakers as decent bargains that one should be able to find a dealer.  ProAcs may be harder, but, they too deserve mention.

There are a few quite decent sounding (to me anyway) speakers that are sold mostly by direct sales from the manufacturer.  They cannot easily be heard unless one can attend audio shows.  The Tekton Double Impacts impressed me for their decent sound at a quite reasonable price.  I also like the Rethm Bhaava speakers I heard at shows.  Much higher in price, but competitive with some really expensive speakers, are the back-loaded horns from Charney Audio.