IMHO i would get an external 5 channel amp to drive the speakers properly, especially if your room is relatively big.
Thanks to all guys. Fixed the problem with my setup. the Yamaha RXV-657 lacks power to drive MA speakers. Got the dial turn just -10dB, and the sound starts to becomes "garbled". Also, IMO not a good match for MA RS. Maybe, as John said - I need to get an external amp.
Had a chance to borrow Sony TA-VA80ES. The difference can be noticed immediately. No longer are the "bad sound" present. Also, the power - oh YES the power. Just turning it for a quarter turn, and the sound is already starting to become too loud for music. That's POWER.
You'll see finesse of sound, finer balance, ... etc.
Still something else is lacking. This Sony's a good receiver, but still lacks the "WOW factor".
Maybe, I'll still have to search for much better receiver.
Again, thanks