Playing devil's advocate for the above, speakers perceived bass response can vary wildly in untreated rooms, as you can get all sorts of nulls that make certain frequencies disappear. My CMS50's bass response can vary quite a bit depending on their position, especially relative to the rear wall. That said, a speaker rated to 50hz isn't going to do 40hz satisfactorily (a lot of people on GearSlutz like the 50's + CMS Sub over just the 65s) and if you're going to spend decent moolah on speakers, spend some money on the room too - it's the biggest upgrade you can give your set up, more so than new speakers or whatever. This is even more important with the lowest octave.
I'm looking to upgrade to the Event Opals at some point (which go to 40hz just fine) but it's faaaaar more important I sort my listening space out with proper broadband absorption first - bass traps, reflection points, ceiling cloud, SBIR, all that jazz.