I am also curious to understand the effect of each change separately. I had this change made. I will tell you this from my experience. IMHO, the "V" config in DSP is TERRIFIC compared to DSP off. However, my reaction to the MAX 40HZ is that my stereo is "boomy". It sounds to me like the subwoofer from hell on many recordings. On other recordings, there seems to be little effect. In any case, I am changing it back on the next service. SO, I have two questions for the sound experts: 1: What is the effect of the MAX v. the 40HZ? 2: How difficult is this for the dealer? The first time they changed it for free. Is it so easy I should expect this or should I reasonably expect to be charged for the change? Thanx all.