I am in the same boat. I just bought a set of Focal Polyglass VRS slim (
https://www.crutchfield.com/S-8HGtyZ...s-100-VRS.html) second hand almost new. They will fit perfectly. The problem is, I also have a set of Boston Acoustics Pro50SE (
https://www.crutchfield.com/S-hJTctB...-Pro50-SE.html) that I have had for some years and as good as the Focal sound, the Bostons are just better. They are 5 1/4 and 57mm deep top mounted. They are just too big without major modification and I am sad that I cant use them. They handle loads of good, clean power. This was why I was reluctant to let me E39 go. If anyone thinks that I can get these monsters in my doors, I am all ears.