there's no need to get rear discs..especially with the weight distribution of this car. you'll just end up locking up the rears. try getting the powerslot rotors or wilwood big brake upgrade and get good pads to go along with it!

 

it is posssible to get the mirage disc's for the rear but your going to have to make your own brackets and or.. take the back ones off the mirage and weld the brackets on to your es... is the only way that I see possible for the es conversion. ALTHOUGH someone here on the forum sells a rear convo kit for the ES... but i forget his name.. just run a search.. he sells them for around 600+