Centralised service tax registration

Dear Experts,

We have centralised service tax registration. Now we are going to made another plant and to be taken another excise registration. In service tax point of view what will be the best option that to take seprate registration or work with same centralised registration. We will be make consolidated balance sheet. What will be consequences in point of view service tax and excise like at the time of filing ER-4 Retrun(Annual Finance Statement).Please advice. 

Thanks