I agree SR7013 is more comparable, but please read again what i wrote. On paper the difference is 15w in 2ch 8ohm which is not really meaningfull, but in real world test there was no difference! Only look at the 8ohm measurements as the 4ohm measurements have been done with the impedance switch on 4ohm which drops power output big time. I can only assume they are afraid to run test with the switch in 8ohm position as they get these from dealer.The SR6013 is not comparable to the AVRX4500. The SR7013 would be the comparable Marantz model to the X4500 and the new Marantz SR6014 is the model most comparable to the X3600.
The power ratings of the SR6-14 and the SR6013 that preceeded it are comparable to those of the DEnon AVRX3600 and not comparable to the power you'd get via the X4500. The difference in wattage is quite large and not just a few watts as you've suggested. It is this additional power that you are paying forif wanting the X4500.
Power Output (8 ohm, 20 Hz - 20 kHz, 2ch Drive)
AVRX4500 125 watts
AVRX3600 105 watts
SR7013 125 watts
SR6013 110 watts
SR6014 110 watts
The SR6014 is effectively the same AV receiver as the X3600 apart from the inclusion of HDAM circuitry and analogue multichannel inputs on the Marantz model and only its porthole display as opposed to the fulled sized display on the Denon.
Marantz declared an output power of SR6013 at 185 W, as did Denon for a 6-ohm load. We conducted measurements for 8 and 4 Ω (setting the impedance selector in the appropriate mode). For 8 ohms, SR6013 power is 151 W in one channel.
2 x 147 W in two, with connecting the next one decreases, but 5 x 100 W and 9 x 50 W are still good results - identical to Denon's. And like the AVR-X4500H, power at 4 Ω is "artificially" limited significantly below the potential of the terminals themselves, especially in the output measurement of a single channel; then it is only 60 W, in stereo there is 2 x 59 W, then 5 x 52 W and 9 x 41 W. Then (in large-channel operation and at 4 Ω) SR6013 and heats up so much.
The noise separation is 82 dB, which is slightly better than the Denon AVR-X4500H. The sensitivity is only slightly lower than the standard, it is 0.29 V.
The frequency characteristics (Fig. 1) are again very similar to those of Denon - the drop at 10 Hz is negligible, and at 100 kHz it does not exceed -1.5 dB for 8 Ω and -2 for 4 Ω. The SR6013, like the AVR-X4500H, can be praised for a clean spectrum in Fig. 2, the strongest harmonic is the second one, but its level is low -91 dB, the third one is still a few dB lower.