The R630v3 offers very high levels of mid-bass and high frequency transparency with rock solid bass. This midbass detail and neutrality comes courtesy of the famous ScanSpeak 8545 carbon fibre pulp cone 7" mid-bass used in numerous mega dollar loudspeakers.
Small to medium sized rooms for music and stereo, but add a subwoofer for home theater. Rears and surrounds for home theater in a large room. Suitable for almost any kind of amplifier given it's high and even impedance. Excellent dynamics and also sounds superb at low listening levels. Made for the seated listener. If you like to get up and move around regularly, the taller R645v3 should be the choice.
For once, a high end audio component richly deserves its glowing reviews. The 630v3 gives up some bass dynamics to the R645v3 but is just fine for average sized rooms.
A sub is not required unless used for very high volume stereo in a large room or for home theater. For home theater systems the majority of users will want a very good subwoofer with the 630v3 since it can operate solidly into the low 30s and can be crossed over well below 50Hz.
Place the 630s several feet out from the short wall, firing down the length of a rectangular room and you will have a superb soundstage.