Hi Jonathan,
I agree with a lot of what Charles and Musicphile say about a quality pre. My preferences not withstanding, I can see the benefit.
You are making some significant changes to your system (have your new speakers arrived yet?). With an opportunity to audition a couple of pre amps around the time I aquired my current Coincident speakers, I actually started getting confused with all the changes that I really didn't appreciate what the speakers were doing until I simplified my system.It is possible one day,I may go back to the Coincident Statement or another 101b tube based preamp. What was just needed was time for the system to settle before determining what each new component and cable was contributing to the sound.
I will say that my system has not had any significant change (other than my source)in the last two years and am VERY happy.
Regards,