If you need a big city hub and like to play in a sand-boxy style, I'd advise for the new box-set + Faces of Sigil (pdf on DT). With that you'll have the city part covered, plus ton of things to do in the Outlands (more than with the original box set).
I have read Planebreaker but don't consider it to be very good, especially compared to something like Sigil. It's a bit too bog standard for my tastes. Other could differ.
I didn't read City of Arches, but I know Mike's work and I'm confident it's as good the rest, so there's a strong possibility here.
For the planar part, it's trickier. The old boxes are really expensive. There's always the DT possibility, but the maps will be butchered. Maybe it would be best to simply go with the quick abstracts of the planes in the DMG 24 + Tales from the Infinite Staircase (the old one — Tales, not Quest), a collection of small adventures from which to draw some interesting things. Well of the Worlds could work, too (but there's a map and the adventures are sub-par). And of course, because a planar adventure could literally take you anywhere, you could very well consider that everything you fancy is a planar adventure. So just take the worlds, settings and adventures you like and stuff them in there.