[Rover]

Hm... only you can say what you need depending on what you shoot. I love the wide angle side of things so I may be biased, but I think that some manner of ultrawide must be present in every photographer's kit, even if it's just the humble Canon 10-18 (which, despite its puny appearance, does seem to be a force to be reckoned with).

 

Before the 17-55, what is your widest lens going to be?