Funny this would come up now after all this time. I pulled my front bar recently and I've been trying to get some stiffer front springs in place... Without the front bar it does seem a little quieter, but nothing major. It's like one layer of say 3 or 4 layers of noise from the front has now been removed.......This car would be an excellent candidate for the Miata springs eq1 noted above. With slightly stiffer rear springs, chassis roll would be reduced a small amount. Road noise in this car seems lower on account of less chassis to suspension coupling points.
edit: fyi, I got those springs installed. I'll try to write something up a bit later...