I'm unbias, so I'm only going to use the three you listed. Since you up north (don't know if it snows in Jersey or not), I would rule out ST1. They are a good system, but made out of galvanized steel and would rust from the salt on the ground. The KW v1 is pretty much the same setup but made with better materials. They are great if you just want to lower your car to your liking, but you wouldn't not be able to adjust your dampening (softness & stiffness). The full solution would be the H&R only if you want to fully adjust your suspension to your likings. So in all, it comes down to your wants and needs, hope this help.
Cobb e30 Map|ER FMIC & CP|MS DP & Stud Kit|aFe DCI|Spec Stage 2+|HRE 840r|CF GTR Vented Hood|OSS Design|Walbro 255|M3 Lip Spoiler|Muteki Anodized Blue Lugs|HID Fog Conv.|Painted Calipers|Bilstien PSS9|Cusco Strut Bar|StopTech Power Slot Rotors, Street Pads & SS Brake Lines|Michelin PSS|Muffler Delete