I think you're already heading in the right direction: audition the speakers you are considering. I compared the DefTech speakers to Paradigm Studios at one time (using a DefTech model that didn't include the powered sub), and switched back and forth at a dealer show room while listening to some of my own music. In the end, I preferred the sound of the Paradigms. To some degree, speaker selection involves some personal taste - especially when comparing different design approaches such as direct-radiating, bipole, or electrostatic - so the best thing to do is compare using your own ears.

With a sub, the Studio 40's ought to be able to serve you very well, but you'll need stands for them whereas the 60's or the Monitor 9's are "self supporting". As for your surrounds, the Atom should be a capable little speaker.