You’re kind of all across the board OP. Want an “E39 feel”, but test driving X6 and XM which are quite different price points and nothing like a 25 year old sedan. Then you’re throwing a povo 530i into the maybe mix.
You’re in the General section here which is across the whole Bimmerpost site. E39 stuff is here:
https://e39.5post.com/forums/forumdisplay.php?f=201
With the way the sizes have grown over the decades, a 3 series is likely where you’re looking. But if you’re prepared to spend XM money, then I don’t know.