what i read is that the human ear basically hears in the range of 20 Hz to 20 KHz , so if a receiver lists 10hz - 100khz, is it overkill or just wasted effort?
What you are reading is called the "power bandwidth" of the receiver. Typically an amplifier will have all but flat response between 20-20kHz. There should be no major variations in the response of the amplifier between those two points when connected to a load resistor. (There are far too many caveats here to begin discussing in a brief answer; that description of frequency response will have to suffice for the time being.) As the amplifier works beyond those two points, the frequency is allowed to dip at the extremes and will usually be designated as the -3dB point in the amplifier's response.
Over 40 years ago Harman Kardon engineers established a power bandwidth for their Citation series which extended the power bandwidth response of the amplifier to five times the accepted hearing range. That gave the "poor man's McIntosh" Citation amplifiers a minimum response from 4-100kHz. According to HK this, along with a few other provisions in the amplifier's design, allowed their amplifiers to better reproduce a square wave within the audible bandwidth. Since a square wave contains all the harmonic content along with the fundamental frequency, it, according to the HK engineers, was a more realistic respresentation of how an amplifier would deal with music than just measuring with a sine wave alone.
This approach to amplifier design has become more or less accepted as one way to build a better amplifier. And, while you will never hear 100kHz and there are more things to be considered than power bandwidth alone, if you are gathering specifications for comparison, I would look more favorably at an amplifier with the widest response.
Unless ...
If you are considering a tube power amplifier, the output transformer typically limits the frequency response of the amplifier. I would still look for the widest bandwidth but tubes are unlikely to match a direct coupled solid state amplifier in this regard.
Finally, I would strongly suggest that you pay little heed to specifications stated on paper. They make interesting reading but tell you little about how the amplifier sounds. The best arbitrator of what to buy is still using your ears and your brain with a bit of common sense thrown in for good measure.