OP
As one of the posters had posted the Pre-amp seems to play a significant Role.
you have done quite well for the room treatment and that is the most important part for the imaging you are going for. The dcs Lina and streamer combo is very good
You will hear the changes distinctively.
Your speaker is top notch and so is your amp. if you think/hear your speaker amp combo is working with good synergy, then an external pre-amp may help improve it. OR you may then spring for a complete separate. Then at that time, I would recommend the gryphon family. I heard it in separate occasions, and I have to say, it is a level of its own
good luck