I'm not affiliated, but I've heard of people looking for some affordable 15x8's for the FC before, and I was among them. Well our prayers have been answered. Rota has just made a batch of Slipstreams in a 15x8, 5x114.3 bolt pattern, 40mm offset and they're available right now. In other words they'll fit with a thin spacer in the front. Here's the best part, they're $550 shipped anywhere in the US. These are limited production, so they won't last forever, but more will be made at a later date most likely. I've ordered mine already.

http://www.18racing.com/wheel_slipstream.html
http://www.preludeonline.com/showthread.php?t=217037

If you're even more picky and want them in a different offset or something, then get 5 orders and go here and they'll make them for you.

http://www.therotaspecialist.com/default.cfm