The best reasons for the Z series, aside from good sound, is their tiny size. If you are going to build a micro system, they are a fine way to go. Like, for an office or area where you have limited space.
Otherwise I would skip the Zpre3. It's a fine little unit, but it sounds to me like you are going to just start on an upgrade path and that maybe that's going to be a stepping stone.
How about a Mytek Brooklyn ? It has a great DAC, very good phono, and acts as a preamp. Often seen used. I own one. :)
Otherwise, how about a Parasound Classic Pre, or P6?