I 100% understand going from fast and sporty to comfortable and luxurious. I went from my 350Z (pretty comfy vehicle anyway) to a 300C. I hated it, but loved the room... It eventually got to me and I traded it for a challenger (current DD) and I am happy with it, but I want more. I think going with an E39 is the right thing, once I sell my RX7, I will be buying an E39 (non M5) because I think it truely will have the right mix of room, luxury, comfort and once I LS swap it, performance.
I hope that the swapped e39 will keep my car bug happy long enough to wait for my son to get a little older where he will want to work on cars with me and we can build something together. In the mean time I can waste money on a welding setup and continue to refine my skills that way.
I think you are on the right track, but just make sure you are getting what you want and not what you are settling for.