Axiom Home Page Forums General Discussion Advice from Axiom Owners Currently at 2.0. What next?

I'd say go with your instincts. The addition that will add the largest change to your current experience, will be some surround speakers.

If you, singularly, are the primary listener, then a phantom center will serve you well. So I'd go with a sub after the surrounds, and take the center as your final upgrade step. (Unless you want to go to 7.1, then I'd add the rears after the center.)