It may sound a little thin in the bass at 8 ohms due to the 3.5-ohm impedance dip - unless there is a room resonance around 150-200Hz to compensate. Normally, a dip below 5-6 ohms would indicate 4 ohms is likely to be best, but room acoustics plays such a big role, it's usually worth trying other impedances.
For what it's worth, Stereomour has a bit more damping than S.E.X.
If 4 ohms sounds better, you can even try 2 ohms!