I would go for the s2k. Even in stock trim you can have a ton of fun with it. It has a built bottom end from the factory so you can boost it without to much of an issue and go up to 500+ whp without changing rods or pistons. The 350z and g35 are based on the same frame and motor so its kinda tit for tat. One is more luxury the other is more sporty but they sound the same as far as exhaust note. Take them for a test drive but don't get the new CR ediition s2k its just plain ricey.