All amps have distinct tonal characteristics as do all preamps. They change the sound when changed, so the answer is: both. Another thing you have check is what happens to the power amp of the integrated when you don't connect it to anything?...maybe nothing, maybe instant destruction of everything you own...so that might be fine (former, not latter), and it would open up a new world of zillions of amp options and matching/miss-matching situations that will lead to possible frustration, glee, bliss, bankruptcy, more A'gon threads, or years of therapy.