Yeah, very lucky haha. Straight and original early model S13's/180s are near impossible to find nowadays.
Massive improvement in front-end stability and turn-in if you install a Nismo Power Brace II or Cusco Tension Bar. Also, install front/rear strut braces. Rigidity wise this is ideal for the street.
I have HKS Hipermax III Coilovers... with 6kg Front/4kg Rear rates. They are a firm ride when the dampers are set hard. From what I've found, going with a coilover that has higher spring rates would be completely overkill for our roads, unless you like drifting. As for alignment adjustability - I have Ikeya Formula rear camber arms, front tension rods (for castor), and rear toe rods.....they really are excellent quality but there are plenty of cheaper options available.
Go with something like that for a basic suspension/rigidity setup and you'll be set. Then down the track you'd have room to install some swaybars.