Hmm, I thought I answered this, but I don't see my reply. Here are the weights:
8 Enkei = 20.50 lbs
9 Enkei = 20.17 lbs
MR BBS = 17.74 lbs
The 9s are .15kg (.33lbs) lighter than the 8s, but still 2.5lbs heavier than the BBS rims. Keep in mind that the BBS rims are listed at $750/ea, so they're quite expensive even used. If you really want a set, I recommend going to EvolutionMR.net and seeing which MRs have upgraded their rims...