I helped my,neighbor, he has and did purchase on my recommendation a pair of large bookshelves (Dynaudio) c-1? Maybe, and a small Polk sub for the lows, his small modest bookshelves w the,small Polk sub, does sound very good, allows him to hit the volume a bit,more with the subs soaking yp the,low freq.
Why I'm not adding a sub to my 2-way monitors for music
I've updated my blog post with more data, more analysis and the conclusion that in my particular case I do not need a subwoofer. I encourage everyone who is on the fence about adding a subwoofer or not to read and comment. I think that either way you'll be able to make more informed buying and configuration choices.
Everyone's situation is different but I hope the post helps you get to the right conclusions.