I agree with what was stated above however to answer your question I will say that Ive replaced a good integrated amp with a good dedicated amp (using as preamp as you stated) and have heard more detail, darker background, better timber/timber decay, better bass response/slam, and improved sound stage. With that said Ive upgraded the dedicated amp two other times and heard an improvement in the above description. Of course one must keep in mind its a matter of diminishing returns! How much are you willing to spend?
Will a Separate Amp Make a Difference
I have original Audio Physic Virgo's running off a BAT VK3ix tubed preamp into the separate amp section of an older Classe Cap150 integrated amp. Using Harmonic Technology cables. Will going to a separate balanced Amp - perhaps BAT VK 250 or Ayre significantly improve the sound? I am not unhappy now but wondering about the benefits of a separate dedicated amp.