Anything from Eibach is good.
Also if your after more the performance side of things I would think the Nismo factory coilovers are the way to go. Only drops your car by 10mm and you don't need to add any camber arms or toes.
However a very good overlooked brand is Tanabe. They do springs thats only 5% more harder then stock. It's made to work with all your factory stuff. So safe long term.
TANABE Racing development 370Z update: TANABE springs, swaybar and underbrace
A few of the big online stores for 370z parts sell this brand.