Welcome!
Does upgrade to you mean more fidelity or more to your liking? Pure single source digital systems may not need a preamp (mine doesn't). Most tubes flavor the sound, so everything has the same "tint". Plus tubes, more than other components, age so the "tinting" changes with time. Lots of other challenges with tubes: noise, micro-phonics, tube matching, etc. Tubes represent the hobbyist end of the audio spectrum.
