My 2004 RX8 clutch failed. It was out of warranty
so I put a Centerforce dual friction clutch in it.
http://www.centerforce.com/

I was pleasantly surprised. The RX8 was much easier to drive
around town as the clutch engagement seemed much smoother.
I noticed right off the bat the pedal force was lower.
The pedal force is already pretty low on the RX8 as the
clutch has an over center assist spring in the pedal mechanism.

Dave Lemon, owner of Mazdatrix, had one in his RX8 and he
does not pussy foot around. He also had one in stock and
I needed it right away. If you need to ask the cost you cannot
afford it :)

No resonant vibrations that I can detect.
No trouble so far and I have had the engine up to 9,000 RPM.

Thanks Dave and to all others that helped me out on this.

Paul Lamar