I believe Undertow might have nailed it. The SWL9.0SE is so accurate and neutral that it is much closer in sound to a solid state preamplifier than a tubed preamplifier. Perhaps owners who sell the SWL9.0SE originally decided to take the plunge into tubed electronics with the Modwright preamp and decided it didn't provide as much change as they were hoping, and they subsequently sold their SWL9.0SE as they searched for more of the holographic presentation of a "colored" tubed preamp. Also, perhaps those who liked the accuracy of the Modwright decided that a good solid state preamp would provide the same benefits while removing the need for tube maintenance.
My reason for selling the SWL9.0SE was the former, although it wasn't my first foray into tubed preamps.
My reason for selling the SWL9.0SE was the former, although it wasn't my first foray into tubed preamps.