Upgrading to Tube; Amp or Preamp

I am currently looking to upgrade my existing system a piece at a time. I currently have a set of Vandersteen 2ce Sigs, VPI mkIII w/RB250 Origin Mod w/Dynavector cartidge, Adcom 565 Preamp, Adcom 555 mkII w/Musical Concept mod, and a Rega Planet CD. I have a rather small listening room, 15x18 w/vaulted ceilings and want to migrate to tube gear. I have heard the Rogue 120 amps and 99 preamp on the Vandersteens and thought they sounded marvelous.

I am into analogue mostly classical, jazz, and some rock. My budget is in the $2000 dollar range and since I want to get as big a bang for the big would it be best to replace the Preamp or Amp. The Adcom gear is a little too bright and the soundstage and imaging are not near (imagine that)what I heard with the Rogue combo. I like the Vandersteens alot but have heard that they get a little too laid back with tube gear. My aim is to put about two to three thousand in my system a year until my wife stops me.

Look forward to the suggestions, oh yeah getting rid of my wife is not an option (ha, ha).