Hi,
Based on your post, there are few things to consider:
1) 18x8" +30 front is very aggressive. A +35 to +40 is preferable
2) 18x10 +25 rear is also very aggressive, but doable with the correct size tire.
3) Running a 18" front and 18" rear generally looks funny. Try staggering the sizes for a better look (i.e. 17/18 or 18/19)
4) Lastly, based on the XRR Website, only a 18x8.5 is available (no 8" is listed). If this is the case, a 18x8.5 +30 will not fit on the front of a NSX without significant body or tire modifications:
http://www.xxrwheels.com/xxr_521.shtml