I think you need to consider bushes. Just fitted whiteline front bushes and it has been the most impressive improvement i've experienced.

 

Whitelines are nice, SPL are better but you can see the cost difference.

OP, I have some hotchkis sport springs going up on the board in the next few days, would be pretty cheap. Here is the stats
http://www.hotchkis.net/350z_sport_coil_springs.html

 

Aren't the SPL's all solid?

 

Yes, and I suggest whiteline for a street car. SPL is great for a weekend play toy, track car ,or something with slammed suspension. Whiteline for everything else. Contact Scott at Fontana Nissan for best whiteline prices. He also sells SPL if you go that direction.

 

Yeah, this is a DD, i don't have a problem with working stock stuff, but it's 70k miles and blown diff bushing, i need working again.

I presume you mean nissanraceshop?