I suspect that the lack of bass some have commented on in the AVI actives might be an issue for the music you listen to. The sub, however, is an additional £800 - but will solve your problem. Perhaps the Neutrons with the sub are a better option. But...buying blind is running a risk, though I suspect the N5s will be impressive.
However, I feel bound to mention, if you're looking at active speakers, the Genelec 8030A or 8040A if you're feeling flush, will do wonders.