What do u guys thins is better the Yamaha RXV-450 or RXV-640??? i think the RXV-450 has more wattage power than the 640 also i has 192K dac & supports prologic IIx & DTS 96/24 but i noticed that the power rating of the RXV-x50 series is rated with 10%THD while the old x40 family is 0.6%THD & i think the lowest THD is better??? so what do u think?? & do u think the 450 is more powerful than the 640??coz i have Wharfedale Diamond 8.4 fronts & Diamond center & they need lots of power @ 6ohm ????? & what do u think is better & more powerful the 450 or 640 or the pioneer D812???