If the driver was designed well and the motor has plenty of strength to control the moving mass, "speed" and accuracy is not an issue. In addition, the box and the rest of the install have a great deal to do with the end result and performance of the sub woofer(s). Think about some of the home audio drivers in 18" and larger sizes that are built for pure clean sound. To relate that to the Icon, there a number of installs with 15" models and their owners have been really happy. There was just a recent build log with a single 15 in a large sealed box and the output and clarity was excellent. So for you, if you feel you have chosen the right model for you, then figure out what amount of space you are willing to give up to reach your goals. Some people prefer single larger driver set ups for their low-freq needs. Others like multiple smaller drivers, in many cases ported.