Please remember that Section 125 Cr.P.C. is for maintenance, therefore, usually it may be expedited in view of urgency of providing maintenance to the wife. On the other hand, Section 498A IPC case is for the alleged offence, and if the accused is on bail (which is generally the case) then the trial will generally be conduced in due course in its turn.
Moreover, the witnesses in both cases may or may not be the same. Further, even if the witnesses are the same, their evidence would be on different issues and will have to be recorded separately. However, you can still try to get these 2 cases heard by the same Magistrate.
Your main ground for hearing of these 2 cases by the same Magistrate can be the ground of convenience to both parties since otherwise both parties have to attend the cases on different dates.