as nismoid said, all your nismo thermostat will do is open completely at a lower temperature than the factory one and it'll just take your car longer to warm up, which in turn equals higher average fuel consumption.. i really never understood these thermostats.
if however you believe your current thermostat is jammed slightly closed then go for it, i'd still put a standard one in there but it's up to you seeing as you've allready bought it. generally speaking thermostats fail by jamming completely open which makes your car take forever to get up to temp.