FF or APSC i wouldnt really see it as such a big deal when it comes to JUST shooting pictures, but if you have the money a 5DmrkII/III would be fine if you have the money. TSE lenses would prob be your best best imo, after reading what other users have suggested. TSE lenses are great for architectural correction so it doesnt look like the buildings are falling back. looking at their options, i only see F4, 3.5 and 2.8 . 2.8 would give you that nice dramatic DOF but i have a feeling those lenses were made a while back, and the newer L series ones would be sharper. unless the old ones are still great. but even F3.5 would give you decent bokeh plus a decent slow exposure.
if you want to add flash and stuff you can always get just a 580exII or 430. (the 430 doesnt have the bouncing card -_-) or you can get some better set ups, soft boxes, etc. the possibility are endless really.