yah, change your rear shock mounts at a minimum... cheap insurance...
I have H&R Sports, and I've driven thumper3ld's car with H&R race springs (very similar rates to IE Stage 3 springs) and I have to say there is a really big difference. I was surprised, but it's like two different cars.
Since yer in jersey, maybe you guys can meet up and (if you ask nicely) he'll let you drive his car. I really liked the way it handled.
The H&R sports are much closer to OE, but firmer. I love my setup because it's well balanced etc. but Jay's (thumper's) is a lot flatter and more aggressive both in and out of turns. Having said that, the ride is relatively harsh.