The reason we say wattage rating have little use is because for 90% of us will never come close to using all the power a receiver can put out or all the power a speaker can handle. A receiver rated at 75 watts per channel driving medium effecient 8 ohm speakers will do so at ear-bleeding levels without working up a sweat in normal size rooms. Speakers with a very high power rating are usually very large tower speakers that are designed to fill a very large room. Receivers with a high power rating (like 140 wpc) is really only needed in very large rooms. lwith ow effecient speakers (86 db or less), or with 4 ohm speakers.
Think of two identicle cars (1970 Mustangs), one with a 120 horsepower 6 cylinder engine and the other with a 335 horsepower V8. If you only go a steady 35 miles per hour to work and back then they will both appear to have the same engine in them and ride the same. The higher horsepower of the V8 is kind of useless. Now, if you're in a real hurry (you like your music very loud) or are driving up a steep hill (low effeciency or 4 ohm speakers) then the extra power (horse or watts) is usefull, needed really.
As for sound quality, if all else is equal (and in reality, it can't be) then the 200 and 800 watt speakers would sound the same at normal listening levels.
As Sam said earlier, ohms and spl (effeciency) are much more important.
Effeciency is measured by giving a speaker one watt of power and measuring the sound pressure (loudness) at one meter.
With a 140 watt Pioneer receiver you can pretty much buy any speaker you want. Low efficiency or 4 ohm.
Here's some reading material to help out a little.
Edited by gene c, May 20 2013 - 05:44 PM.
"Everyday room": Panasonic 58" Plasma, Dish HD DVR, Pioneer Elite vsx-23, BDP-23 BR, dv58avi universal dvd player, Paradigm Studio 20 V1, CC-450, Dayton HSU-10 subwoofer.
"Movie/Music room": Toshiba 65" DLP, Dish HD receiver, Marantz 7005, CC-4003, BD-7006, Polk LSI25's-LSi7's-LSiC, 2 original Dayton 10" "Mighty-Mites" subwoofers. (subject to change without notice).
Also have MB Quart Vera VS05 +.....too much to list. Help me.