Yes, I did listen. And was able to sell my Ayre K5-XEmp (a very good unit and highly recommended for anyone who needs a pre amp). If one uses a single source with a good method of controlling volume and a good output stage, adding a preamp will only make the system less accurate. As long as folks accept and understand that under the above circumstances adding a preamp is adding distortion, then I am fine if they prefer the resulting sound.
But ultimately, if accurate music reproduction is the goal, having the minimum (to get the job done, notably controlling volume as transparently as possible and driving the interconnects and input stage of the amplifier optimally) amount of parts in the signal is desirable.