In my experience the preamp has an incredible sound impact.
I upgraded from an integrated amp to preamp and amp in two steps.
I first bought a tube preamp (McIntosh C 2600) and it took over the preamp duties from my NAD C375BEE. I was shocked on the impact.
I was able to 'audition' it at home and the improvement in preamp was audible using tape deck, turntable, streamer and burned CDs.(tube preamp has phono stage and DAC built in).
I then bought a MC 302 McIntosh amp and it was an improvement but I the preamp was the reason the journey was accelerated. I think its about 65/35 split.
I can't answer Q2.
I upgraded from an integrated amp to preamp and amp in two steps.
I first bought a tube preamp (McIntosh C 2600) and it took over the preamp duties from my NAD C375BEE. I was shocked on the impact.
I was able to 'audition' it at home and the improvement in preamp was audible using tape deck, turntable, streamer and burned CDs.(tube preamp has phono stage and DAC built in).
I then bought a MC 302 McIntosh amp and it was an improvement but I the preamp was the reason the journey was accelerated. I think its about 65/35 split.
I can't answer Q2.