New preamp: need to change speaker placement?

Yes Tholt it may. I replaced the caps in my pre and found moving my speakers was the final step to fine tuning. The new caps were much more alive and dynamic so speaker placement fine tuning was needed.

You might have to move them, I changed some power cords, and I had to move speakers some, the center image had shifted.

I too use a masters approach to placing my speakers. I move them and then listen. I move them and listen, I move them and listen. When I like the way they sound I quit moving them and just listen.

No stinking computer program is going to tell me what sounds best..

There is, theoretically, a place in a room where speakers interface at an acoustic optimum. A computer program can help find those locations, but there are too many variables for the procedure to be absolutely perfect. Human hearing being what it is, we will want to final-tweak them to the location where our ears tell us that they sound best.

Once you find what seems, to your ears, to be the ideal location, it's probably best to do some extensive listening after each component change to allow your ears to adjust. Unless there has been a change in the acoustical environment of the room (by adding a piece of furniture, etc.), optimum speaker location really shouldn't change.