Markw gives excellent advice...
But of the two options you've given, the HTR5660 is far superior IMO...I'm not a fan of anything that posts specs of:
100W x 7 (8 ohms 20 Hz-20kHz, THD 1.09%)
That would just scare me.
The yamaha will deliver clean, dynamic power. I think most here would agree that 85 watt Yamaha receivers will top any 100 or 110 watt Sony receivers for sound quality and true power. I doubt the Sony's power supply could deliver that much juice for an extended period of time.
The 5660 is an excellent receiver.