I've got one that I'm using with an LFM-1, and I've got some detailed comments here . How much difference it makes will depend on your room and how it is employed. A well-behaved room or one with lots of frequency dips (which are hard to fix with any form of EQ) may not yield huge differences, while a room with peaks can be much improved with just a little effort. My room was fairly well-behaved, and I did notice an improvement with the SMS-1.