Which cat-back system should I get?

I read some stuff from CarReview about the 5Zigen Fireball....sound very good to me...

Click here to read the reviews

Summary:
This cat-back has in my opinion the best sound of anything on the market. Nice low purr, and when under stress at higher rpms sounds even better. Takes about 2 weeks for gaskets to seal and get the full sound out of it.
Installation is straightforward and made easy by the design of the cat-back itself. The 5zigen sits nicely under the rear section of the car, angled slightly for an agressive look

Strengths:
Noticeable increase in power. (esp. in 2nd, 3rd gear)
Great sound, very low.

Weaknesses:
None yet.