Thanks a lot everyone. I definitely think a 2.8/21 is on the cards by the end of the year. I don't mind the size of it, in fact I quite like the way it looks. I don't think the 2.8/25 is available in ZE form, I could be wrong, though.
I think I'd like to end up with: 21, 1.4/35, 1.4/50, 85...