Are you absolutely sure the speakers are set up properly? Before spending money on a new preamp I would investigate speaker placement, toe-in and more critical with Vandersteens than most, tilt angle.
When I owned the 2CE sigs a while back it was amazing how dialing in speaker set up made them go from adequate to superb. And sometimes it can be as little as a couple degrees toe-in or tilt angle.
When I owned the 2CE sigs a while back it was amazing how dialing in speaker set up made them go from adequate to superb. And sometimes it can be as little as a couple degrees toe-in or tilt angle.