Its the suspension that makes most difference .You need to change that as springs on their own will not help altough both would be better.
You can use any aftermarket GTR units for the front but the back MUST be stagea. ( they are different shape and stronger as its an estate) If you can get them rs260 units are probably the best for front or back or teins etc but must be for a Stagea.
Decent suspension will change the car more than you would think but you cant expect the same comfotable ride with sports suspension.