sounds like you are pretty fast but as said before don't sacrifice speed for technique. My kicks are a slower than yours but they are extremely powerful i kick harder than anyone i know but i cant really do it in rapidly. I am a power fighter so i like to plant the feet get a strong base fire off short powerful combinations. lots of times when you throw them rapidly like that you lose alot of power as your base becomes more and more unstable. be sure that you keep your technique and speed will come.
"The fat man flies at midnight"