Really? How did you come to that conclusion? Did you measure it?
Well I did (see
power measurements) and found it to do 116wpc at 8 ohms 175wpc at 4 ohms, 2 channels driven at 0.1% distortion without holding the line voltage constant. In addition, it had a very low output impedance (under 130mohms,
see measurements up to 20kHz for a receiver).
The SNR was also very good (> 81dB @ 1 watt, unweighted and preamp included!),
see our tabulated measurements.
I know, but you're probably gonna say, "What about ALL CHANNELS DRIVEN?"
Well here is my reply
The All Channels Driven Fallacy Dedicated Forum
The ALL CHANNELS DRIVEN Editorial
In any event, the RX-V4600 has some pretty decent amps for a receiver with plenty of headroom to earn it a THX Select2 certification. If you are running inefficient (<89dB SPL @ 1 meter) 4 ohm nominal impedance speakers in a reasonably large room (greater than 2500cuft), then I do recommend an external power amp, at least for the 3 front channels (L,C,R). But I would also make this recommendation for any sub $3000 receiver.
Regarding choosing between the RX-V4600 or RX-V2600
I would pick the latter in a heart beat simply b/c of:
1) HDMI Switching, Scaling
2) Cheaper price
3) Likely at least as good amp performance as the 4600 which is what I am told by Yamaha. Though we will confirm this in a formal review soon.
I hope this helps.