I've found this website (WillTheyFit.com) is one of the better sites for determining how new wheels & tires will fit compared to the original OEM setup. Gives you an indication of whether a spacer might be needed to get a look close to the factory geometry.

I also see by your post above that you highlight the new rim as a 6-spoke design. But the Niche Vicenza M152 is not 6-spoke design according to the website. Just saying.