What can I expect from these mods?

Inspector71

I apologize if this has been asked a zillion times but thought others new to this car might have the same questions. I have a base model 2009 370Z, red with spoiler package. Based on what I have read on this very informative forum, I was thinking of going with the dual air filters (best brand?) headers (best brand?) and the Stillen exhaust system and mufflers. What should I expect to pay for this and what kind of horse power should this set up generate above the stock 332 hp? Finally, if the top speed is limited, what would be the value of these mods? Could they improve zero to 60 times and are there other benefits? As to what I am after, it is a daily driver, I don't plan to race it, but I would like to get the best from this great car. Thanks in advance.