i have the sig's w/ no sub, very good electronics. my opinion is that a sub is only indicated if you are a bass freak or really like to crank the volume. the 2ce's are true full-range speakers, natural-sounding and honest. i have two different friends who upgraded (one to the 3 and one to the 5) and they have both had trouble integrating and driving the big speakers, as their rooms are not mansion size. also, i am not sure the signature's are "better" than the regular 2ce's - they are brighter, which is not necessarily a great thing in the world of cd playback. the bottom line, in my opinion, is that the 2ce's deliver everything needed for satisfying music reproduction at a reasonable price. unfortunately there is no need to upgrade .... but we do it anyway, as we are "audiophiles."