I replaced my stock flywheel with a fidanza unit which is only 8 lbs...it made a huge difference in acceleration, but made it harder to launch. it took a while to relearn drving it to be smooth when shifting(Bucking?). Flywheels are worth the money imho. The stock unit is 18 lbs so anything you shave off will help.
Go with the lighten flywheel. The previous posts states that the "revs" will be faster and launching the car will be an adjustment. In 2003, I will swap out my flywheel and clutch, I'm looking forward for the "new excitement".
For the money, I'd go with the Fidanza. As for shaving down the OEM I wouldn't bother. You won't get it down far enough to be worth the expense and have it still be safe. Ask JGY about it www.jgycustoms.com. He used to shave OEM ones down pretty light for cheap but he quit doing it because he said the metal isn't consistent enough. He'd get one down light and you could bend it by hand, other times he'd get it to the same weight and it'd be fine. So I'd stay away from lightening stock ones.
Yea, I second that. The lighter flywheels are engineered for that, which means they are tested and redesigned and tested etc until it works. Lightening a stock one that is not made to be that light will run you into trouble.
The cheapest I've seen it is at www.importperformanceparts.net
For the '91-'96 GA16 it's $309 and it doesn't give the weight for some reason. Then for the '91-'99 SR20 it's also $309 and weighs 8.5 lbs. Shop around though for the best price.