I've been looking around a little at Ascend, Athena, Axiom, PSB, Energy, NHT,
for speaker system for my (HK) AVR-525, and ran across this website.
If you are wondering how a bookshelf compares to a floor stander, or how
different brands compare, check this out. I don't know much about speakers
yet, but I think the graphs showing frequency drop-off and THD + Noise
might be relevant if you have narrowed down your search but can't make up your mind.
http://www.audiovideonews.com/speakermeasurements.html