Lighter flywheel, wheels, crank pulley etc usually make more of a difference in the lower gears. The power gains tend to get less and less as the gears get higher. Fidanza had a good description of this on there web page with some charts showing the diminishing power gains as you went from 1st to 4th gear, but I haven't been able to find it recently. On the dyno, I haven't seen much of anything for gains out of lighter crank pulleys and flywheels. Putting more air in your tires can give better gains on the dyno than a lot of mods.
I would recommend a lighter SFI Spec 1.1 flywheel like the 12lb ACT just for safteys sake though, if your making some decent power. Seen too many flywheel explosion pics on DSMs the last few months.