PrimaLuna Preamp Upgrade Question

I did exactly what you are considering. Was a PL owner for years. Prologue 2 integrated to Dialogue 2 integrated. Then decided to go separates in phases and bought a used PL preamp and ran it through the Dialogue. It was a lateral move. Then bought a PL power amp and sold the Dialogue 2. Used it for a few years. What jbhiller said above was my case. I bought a 6SN7 preamp and 6C33C based mono blocks and quickly sold the PL amp and preamp. In my system the 6SN7 preamp made a big Improvement in sound. More open and natural. Separates offer me more flexibility and I have a separate backup amp and preamp should they be needed. Both my main and backup preamps are 6sn7 based. My system is here on Agon. I finally arrived at the sound I want. It is customized to my ears. I am extremely happy and greatly enjoy my lps and cds. Good luck and have fun! 

Getting to the sound you want takes years in this hobby. It requires time to evaluate synergy between components. Don’t be afraid to go out on a limb or try something out of your comfort zone. Reviews and sales folks are helpful but only you can decide. And a component can sometimes cost less, be based on older designs, and sound better than what you currently have. But the main thing is enjoy what you have because it’s about the music. The equipment is just the means to the end. The emotional music experience and artist’s statement through their art is what you are after (me anyway).