I am sorry this question has not been addressed sooner.
Firstly you have the option of shocks and springs or a complete coil over setup. With the springs obviously its the cheaper option as opposed to the coil overs however with the coil overs you get a large range of customisation.
To answer your question. With springs there are a range of manufactures that offer products for the ST185 GT4, all with respectable reputation. Tanabe, TEIN, King Spring, Eibach and TRD to name a few and KYB, Tanabe and TRD make shocks to compliment the spring setup.
Coil over setups are offered by D2 racing, TEIN, BC Racing, Megan Racing and a few other but these are the main ones that come to mind.
You probably know the coil overs are going to offer you a more custom setup for your car I.E. ride height and stiffness that you don't get as much with the springs and shocks but at the price reflects this of course.
My personal advise would be if you are going to use it as a daily as well as track work then get a set of KYB shocks and complement it with TEIN S Sport Springs.
Hope this helps.