Hard to brake in my 2006 Magnum R/T AWD

So I picked up a Magnum ( Always wanted one) and the car I found is clean/low miles but needs sorting.

The brake pedal in the car is firm but takes a great deal of effort to actually stop the car. I had assumed this was a faulty brake booster but I'm sad to say that after standing on my head and swapping it out....that did not resolve the issue. The car appears to have new front rotors and pads. Not sure what else to investigate but the front brakes look really new and I'm wondering if the rotors were not cleaned or some other issue that could have glazed the brakes. Does this make sense? Are some pads just really crappy? Interested in recommendations for what else to try. I'm thinking about running a DA sander on the rotors to assure they are not glazed and maybe sand or swap out the brake pads. Any other suggestions? Doe this plan make sense and if so are there preferred pads for the magnum?

Thanks,

Will