Shifting center image and recommendations on an approach

I am a relatively new member of Audiogon and this is my first post. I apologize for the length of this. I’ll get better in the future. I’ve had the same system for many years and recently upgraded old Dynaudio speakers to Focal Aria 936. I’ve had them for two months and have struggled mightily with placement. For context, I have a Rotel pre-amp and amp (both older) and a Bluesound streamer. I also have an off-brand integrated tube amp (Yaqin).

I continually experience a shifting center image. It is primarily skewed more to the right. I’ve used the usual test songs such as Ballad of a Runaway Horse (as well as others, including 3 people Describing Position On Sound Stage in Stereo). The strange thing is that I hear the center image shift over to different positions across different listening sessions. I’ll adjust the speakers slightly to regain a center image, come back and it will be back to right or left. I eliminated the speakers as the problem by hooking up my old Dynaudio’s and experienced the same condition. I switched outputs on the pre-amp, also resulting in the same condition.

Well, today, I hooked up my integrated tube amp and I no longer experience the problem. Image is center and overall soundstage is good. So, it would seem to be a problem with my old Rotel pre-amp. Apparently, I must have been dealing with this for a long time and only became aware of it once purchasing new speakers and being more intentional about the soundstage. Ironically, I don’t hear a significant difference between my Dynaudio and Focals – I’m comparing each at this point.

Here’s my question (sorry!). Have others experienced a similar situation and how did you resolve it? And, I’m interested in opinions regarding returning the Focals (I’m within the period to do so) and getting a better integrated amp OR keep the Focals, knowing down the road, I’ll upgrade the integrated amp, thereby (hopefully) realizing the greater potential of the Focals?

Thanks very much in advance