PrietzOr's has got it 100% right
the difference between the SC-71 and that Marantz amp is absolutely miniscule! if you want the math - 10 watts more power will give you a "whopping" 0.3 dB more volume at full power
that's less than the knob volume adjustment - 0.5 dB.
I'll give you the why later in this post.
xhattan, it's your money and your choice. but I stand by my original comment to you that if you want an ext amp, get one that has substantially more power than the receiver's amps, otherwise IMO, you are wasting your money.
the tests show that both amps show similar power 5 & 7 ch driven at once.
and you are not completely correct than a 150 w AVR will dip to half it's power all ch driven. it all depends on 2 things:
1. the size of the power supply
2. the type of amp
class D amps are close to 90% efficient while class A/B amps are about 50% efficient.
so all things being equal, Pioneer is one of the few AVR's that actually can hold much of its rated power all ch driven as opposed to the typical AVR with class A/B amps.
and I'd have to agree with PrietzOr again that your KEF's are not that hard to drive or inefficient. if you want to talk hard to drive, inefficient speakers, try Magnepans - only 85 dB efficient and 4 ohms. they do need power/current to "come alive".
and guess what - there are quite a few here who successfully use Pioneer AVR's on Magnepan setups, myself and DonH50 included
the only thing I have done is use an ext amp for the most demanding Maggies, the 2 fronts which are very large 2' wide, 6' tall panels. and the amp I use is rated at 300 w @ 8 ohms / 600 w @ 4 ohms. so there's no question it's more powerful than what's in the receiver
I use the Pioneer for the Maggies used as surrounds & center.
your KEF's should pose NO problems for the Pioneer.
as far as volume...what you think you experience is probably not what's really happening
you think you need to turn the volume that far up because of limitation in amp power. actually, my experience with the monster super-flagship SC-09TX and SC-68 is that it's the preamp
levels MCACC sets that cause the volume to be needed turned up as much as it does.
proof - I've owned 2 former Pioneer Elite flagships based on class A/B amps - the highly rated VSX-49txi & 59txi. the MCACC calibration in both set the channel levels exactly 6 dB higher
than what the ultra high powered (1400 watt total power) SC-09 did. the result - when I used to listen at -15 with the 59txi, I now have to turn the volume up to -8 with both the SC-09 & SC-68. the MCACC in the class D receivers is tuned differently.
in this case, the volume setting has little to do with the amp power; it has a lot to do with the channel levels set by MCACC during calibration. you can raise the overall volume just by bumping up every ch level manually in the MCACC speaker settings. why Pioneer has tuned the newer class D amps this way I don't know but my guess is that it's to keep the preamps from going into clipping.
my own results taken from the same mic measuring position are consistent that both class D AVR's I own are tuned about 5-6 dB lower in volume than the older class A/B AVR's from the earlier 2000's.
my guess is that if you buy that Marantz amp, it will make negligible difference to the volume level
& then you'll come here asking why you still have to turn the volume to the same setting
even if you did notice a difference, here's the mathematical truth behind amp power:
it takes 10X
the power to produce 2X the volume level. here's the formula so you can do the math yourself.dB difference = 10 x LOG(power1 / power2)
here's an example which will be what a lot of people adding an Emotiva XPA amp to a decent receiver are going to get:going from 140 watts to 200 watts = only a 1.54 dB increase!
and that meager 1.5 dB is only at MAX power output
not when the amp is normally cruising along at few watts tops. so buying a 200 watt amp will be the same as turning up the volume a mere 1.5 dB, pretty big difference, isn't it?
and 1 dB is the point where a volume change just becomes perceptible to most people.
IF you have future plans to get better speakers which are much more power demanding, less efficient or 4 ohm rated, then getting an ext amp can make sense. but when that time comes, look at something substantially more than your receiver, something in the 200-400 w range to make it worth your time & money
that Marantz was really made to go with their prepro's for people who want separates, not so much augmenting receivers. to augment receivers, most people would probably look at least getting 200 w to do some good Edited by ss9001 - Today at 5:46 am