I have the Stokke Explory, and it doesn't exactly go down small. When it comes time to change the E91 though, I will be going for a 5-series. The 3 series just simply isn't big enough, even in touring form. I mean, we can get the frame and the seat in, and the car seat will fix to the frame, but beyond that, you can just squeeze the umpteen bags of nappies and clothes and stuff you need to take with you, leaving little (read:no) room for shopping or anything.
On the other hand, I did buy a Range Rover, and that has HEAPS of room in it. Easily swallows up all the kid gubbings, and a decent shop at costco to boot. Without breaking into the cabin.
If you do end up shifting the E90 for more room, the E91 will just be a disappointment for you.
530d M-Sport Touring.