I have had my Yamaha 640SE for about a year, which sounds excellent at high volume levels. However, unfortunately I still live with my parents so I dont get to crank it up anywhere near the volume i'd like! Not very often anyway. The Yamaha delivers excellent sound quality through my Mordaunt-Short Avants when I have it loud, whether it's with movies or music. But when I use it at fairly low volume, it looses the quality. I am therefore thinking of upgrading it. Obviously, I need an amp which sounds excellent throughout the volume range. I am interested in the Marantz SR7500, which will be available shortly. Can anybody recommend any suitable amps up to about £600. The only other worry I have is that my room is quite small - only about 4m square. Will a more powerful amp be too much for the room? My speakers are MS Avant 906 fronts, 905 centre, and 902 rears. Any help would be great!