Unfortunately, there are no single point of sales for all three (Rolex, AP and PP). The Hour Glass is the only retailer to have all three brands, but not in the same store.
However, I think you can forget about getting an AP from THG (unless Concept, full diamond or quartz pieces). AP is changing its dealership model to be almost exclusively boutique only, so just go THG or Cortina for Rolex and PP, and the boutique (MBS or Liat) for AP.
Also, if the collection you're thinking of starting is GMT Pepsi, Daytona, Nautilus, Aquanaut and Royal Oak, I think can forget it.