It seems the Denon 4000 series can handle 4 Ohm better than 3000 series. From S&V measurements the AVR-X4200W offer 216 W into 4 Ohms, 2 channels driven, 0.1% THD, while for the AVR-X3400H it is 145 W. Both are 7 channel receivers, but the successors to X4200W (2015 model) now have 9 channels of amplification, so I'm unsure if the successors handle 4 Ohms as well.