Number of channels vs. power when using fewer

Boomzilla -- Sat, 01/16/2010 - 00:49

 I'm AVR shopping.  There is little price difference between most manufacturers' "best" 5.1 channel receiver and their "least expensive" 7.1.  Assuming that a 5.1 and 7.1 receiver are both rated 100 watts-per-channel, and if I plan to use three and only three channels, will the larger power supply of a 7.1 receiver provide more current than the 5.1?
I understand that as more channels are driven, the effective power output per channel drops (this is why the manufacturers so rarely rate their receivers with all channels simultaneously driven).  I've never specifically read this, but it would seem that the power supply would be the effective limitation on output.  Therefore, in theory, the larger power supply of the 7.1 receiver would provide more current to the three active channels than the smaller supply of the 5.1.
Also, assuming that all other factors are equal, is it worth the extra money to buy the least-expensive receiver rated for 20-20K power output rather then the most expensive one rated at 1KHz?
Thanks - Boomzilla

Boomzilla -- Tue, 01/26/2010 - 04:12

 I posed this question to several local (and relative knowledgeable) salesmen and their comments are summarized as follows:
Yes, in theory a larger power supply would allow better performance with fewer channels.  The power supplies of commercial AV receivers, however, do not necessarily increase with the number of channels, but rather with the price of the product.  This means that a company's best 5.1 channel receiver (priced at $400) has the SAME power supply as the same company's least-expensive 7.1 channel receiver (also priced at about $400).  
That being the case, the ONLY way to obtain better wattage performance is generally to buy a more expensive product.  The exception, as agreed to by numerous salesmen (who did not sell this product) was NAD.  NAD apparently rates their products with all channels driven (unlike anyone else).  The prices of NAD equipment, however, are equivalent to what you would pay for anyone else's product with similar power performance.  (In other words, the 75-watt rated NAD receiver would have amplifier sections equivalent to anybody else's 150-watt rated receiver - and both would cost about the same).
The information above seemed to be "common knowledge" among the consumer electronics salesmen whom I interviewed.  They may be wrong, but their claims sound plausible to me.  Your comments?

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