I have two sets - one with a 3w, 5w, 7w combo and the other with a 4w, 7w combo. I notice the difference between 3w and 4w - but more importantly its nice to have a 5w that you can play out of short rough. Frankly I am shocked at the number of times I see people use a 3w out of crappy lies.
Very few courses around here have fluffy sand in bunkers. I use a 58* or 60* wedge (depending on the set) for all my greenside bunker shots and rarely wished I had a SW instead. IMHO it is often a mistake to use a SW in bunkers for many of the courses in this region. That being said, I have a 56* SW in the garage in case I feel that I need one.
Just pointing out that there is no "correct" answer to this question Les, and it is far from a "no-brainer". People have to evaluate their own game and the type of courses they play when choosing their equipment setup. I find that its always useful to have a few "extra" clubs at home in case you want to switch things around a bit.