I recommend CAI over SRI
I have to disagree with Gofast and Thejeans.
I've run both the SRI and CAI on my Mazda3s and they both give a significant improvement in performance and sound. Additionally, they seem to smooth-out the throttle response in the 3k-4k range.
Using my calibrated butt-dyno, I would say the SRI added about 5 lb-ft of midrange torque and maybe 3-5 peak HP.
The CAI seems to be close to double that, with around 10 lb-ft of midrange torque (3k-6k rpm) and maybe 6-8 peak HP. Believe me, I was totally surprised how much difference the longer tube of the CAI made.
The thing to remember is that what most of us feel is mid-range torque. Peak HP typically happens just before or at the redline, so it's really almost unnoticed.
Whenever you look at dyno charts, unless racing is your goal, look at the power and torque gains in the 3k-6k rev range. That's where you'll feel the difference.