lug nuts hold the wheels on the car - don't take the risk of forgetting to tighten the aftermarket ones. Get the OEM spherical seat lug nuts.Im toronto as well, just bought my itrs as well and looking for spacers now and lugs haha. anyways you cant run aftermarket lugs because they are conical lugs and their pattern will not bolt on very good to your "stock" (read:itrs) wheels. you will have to retighten them every few weeks. you can run them ofcourse but its not recommended because they loosen fairly quickly.
you should run 25mm spacers to make it flush with your car and if you buy the right ones you wont have to do any adjusting just plug and play. right ones: h&r, project kics, etc. i know teknotik sells project kics for 320for 4 maybe if we buy em together for cash we can get a deal. let me know!