I have a relation who has just bought a pair of Zensor 3s in the last 5 weeks and he talking about selling them and buying the Zensors 7s, the question is he's expecting a big increase in his music, not forgetting he also runs a BK XLS 200 sub. Personally I think he should run the 3s in more and see what he thinks is missing from his current setup with the BK XLS 200.
My thoughts are he will get a bit more bass from the 7s but not enough to satisfy his door shaking requirements on the bass he likes.
I personally think he wont be happy with the 7s as he wants a big increase and I don't think he will get it? I could be wrong as I have never heard the 7s and another option he mentioned in Monitor Audio Bronze 6s
The rest of his system is as per my signature, and I'm perfectly happy with mine