I'm going relatively inexpensive, but light. So Enkei PF01 in 18x7.5+45 (17.6lbs) and Hankook R-S3 225/40-18 (23lbs). The interesting thing is the R-S3 in 225/45-17 is 2 lbs more.
I'm hoping I can stay about the same weight as the stock rims which means I'll only be gaining 2lbs with the new tires. I was also considering the OZ Aglitteraatilpiterattaa..... rims, but I like the look of the PF01s better and they're only .4lbs heavier.
I was also looking at some sweet Enkei STI rims that were on the JDM STI Legacy, but I couldn't verify the weight and at $200 more per rim I wasn't willing to risk them being over 18lbs.