Running 2 vBulletin Boards

[Wordplay]

I'm currently running a vbulletin board and a website, that i manage and well get payed monthly for maintainance... all that's included is my hacked vbulletin 3.0.3, 4images gallery and vbandvanced, main feature being the events, going to the forum to talk about them and whatever else, as well as uploading pictures to 4images gallery.

now, i'm supposed to set up a new website that works the EXACT same way just with an in my opinion "similar" cause (the site i'm currently running is an asian parties website and the site i'm going to start running is a hip hop events website - but both in the same city). i've already decided on using the same members list.

now what i want to know is. what would be better... to set up the site completely new on a completely new domain. or to upgrade my domain and install a second vbulletin and a second 4images gallery on that site? is that even going to work?