I have to disagree, I don't think you will be able to make that work. Plasmids are already quite high copy number so going 2x higher is not going to change your level of drug resistance in any practical measure. In fact even one copy on the chromosome confers resistance nearly indistinguishable from a plasmid. You really need to have one of your plasmids with a different selective marker.

I agree with Michael, usually when manipulating e.coli, the same concentration of antibiotic is used for single chromosome integration and high copy number plasmid (e.g pUC19 will still be selected with same ampicillin concentration) therefore this will not be practical. Having said that you can try to have both plasmids together but you will have to conjugate the other one in (this requires screening by PCR after plating for single colonies) since conjugation frequency is very high you will find cells that might harbor both plasmids, however, this depends to high degree on the stability of the plasmid without external selection selection and in either way is not recommended therefore as Michael suggested the easier solution is switching the resistance marker.