Thanks cschang and Dudley for receiver's info!.
And you're right, manufacturers of today's receiver are better to go to that direction of allowing consumers that nice feature for better fine-tuning. For 2.1 mode, I like to be able to lower that LFE cutoff frequency of 80hz further down, not that I'm against with THX specified norm which is perfect for a type of application like the Vents which has its center channel lowest frequency response down to 80hz but for other speakers which are bass capable eg. freq resp of 50hz, that high frequency like 80hz or above lead to directional perception. 100hz is average, 80hz is good and lower is excellent, at least in my own opinion.