If its between Q500 & Q700 then consider the following factors:
1) Room size ( < 200 Sq Ft Q500, for bigger area Q700 will be better as far as 2.0 setup is concerned)
2) Damping factor of Amp at 20Hz (Q700 behaves well with highly damped amp output stage, reason being the two ABRs)
3) Sound stage (Q700 has a bigger sound stage)
1) Room size ( < 200 Sq Ft Q500, for bigger area Q700 will be better as far as 2.0 setup is concerned)
2) Damping factor of Amp at 20Hz (Q700 behaves well with highly damped amp output stage, reason being the two ABRs)
3) Sound stage (Q700 has a bigger sound stage)