I currently own the 4B-ST, and have done a bit of A-B comparison with the 3B-ST. If you have large main speakers and like to listen at moderately loud levels, or you listen to music with a lot of deep bass content, then I believe the 4B-ST is worth the extra money. Otherwise, the 3B-ST is an excellent alternative. Since you are posting on this board, I assume you are willing to consider the purchase of "new demo" equipment. I got a superb buy on my 4B-ST from "Bestofdeal", a clicks-and-mortar audio business in Santa Clara, CA. I suggest you contact the owner, Danny Oovlin. The easiest way to contact him initially is by E-mail at his business address: [email protected] I found Danny to be very professional, and I intend to buy several more pieces of Bryston gear from him.