Yes, worth it. Agreed on the smooth tubes to compliment, but you will still see gains without them.
From two different 370's of mine: first is a 2010 comparing K&N vs paper filter only; second is a 2011 comparing K&N+Cobb tubes vs paper filter.
Eventually I will be trying a set of the pop chargers, which have nice built in velocity stacks -- HOWEVER, this will be in conjunction with custom made fiberglass airboxes. This will be a late summer project, so expect no updates before mid July.
There's nothing wrong with the Nismo exhaust as an upgrade from OEM IF you can pick it up on the cheap (say < $550 shipped; < $350 picked up)