The point I think most of us are trying to impress upon you is that even if you're only lowering the car for aesthetics, you should consider products that are engineered specifically for the ITR.

Also, keep in mind that any aftermarket spring set is going to be stiffer and will negatively affect ride quality.

You seem to have some contradictory goals in mind; I'd hate to see you lose money by going with some no-name eBay brand springs only to realize that you were better off keeping the car stock.