I just installed a Kinetik HC1400R in my 09 Civic Si. The install was simple, with just a little trimming on the plastic base battery tray. It fits beautifully and works great.
I'm running about 1400W max of amp power and didn't want to have dimming issues. I was told by Audio Que and Kinetik that as long as I was cranking everything to the max, I shouldn't have any power issues with my stock system. Following their advise, I have had no issues what so ever.