Tripp...The C500T or C500P is quite a step up from the C2300 and current C2500. The C500 is a fully balanced pre-amp, each channel has discrete isolated electronics. The power supply and controller circuitry is in a seperate chassis.
A preference for tubes is a matter of taste. Tube rolling allows you to alter/tweek expression and inject a little listening magic into the presentation. For me, tubes can bring me closer to the musical reality. Others argue that they can raise the noise floor in a negative way. That is true too, but most will agree that having tubes somewhere in the chain is generally more musically satisfying!
Just last week, I unboxed a C2300 and a pair of MC600s for a friend. The combination did sound great! If you can find a used C2300 or ex-demo, I'm sure you will be happy with it for quite some time. IMO, the C2300 will be more desirable on the used market than the C2500 longer term also.