Just curious, how do you plan to split those contacts between company (global) phonebook and private phonebooks?
I mean, thirty thousands is a medium city population, even for a 1024 SC PBX is quite a lot. Assuming you and me are registered to the same PBX, do you know who Andreas Stavrapopoulos is? Or Clara Bunacci? You don't. So, putting these two in the global phonebook not only make no sense, but also will slow down your extension. These should be in my private phonebook. On the other hand, company's dentist, pizza delivery, taxi, better be in the company phonebook.