My hobby car is the Integra, i used to only upgraded the front with NSX rotors and calipers, it does indeed provide much more braking power, but it horribly upset the braking bias/balance. I later on upgraded the rear with RSX Type-R ones to gain the original brake balance back and is much nicer... the car doesn't "dip" anymore.
The same can be said for the Mirage. If one upgrade only the rear, they can potentially lock the rear tires up in the rain and/or have undesirable effect... Anyhow, if you or anyone else drove their Mirage, and they feel that the brake bias is not to their taste, obviously they can tune it to their liking, maybe upgrading the rear only... but the potential risk should be mentioned imho.
PS: Is normal to have a "front bias" brake system, because it is easier to control and the added weight shifted to the front gives better traction for cornering (up to a point until the tires grip gives).
Is good to know they are direct bolt on, I may upgrade both of them in the future, thank you.