The upgrade path that makes the most sense to me is shown below. I would make improvements in this order, putting the upgrades that make the most audible improvements closer to the front of the list.
Something else I would highly suggest is to add two to four subs in a multi-sub configuration. This is an upgrade that should probably be ranked ahead of all those listed above, in that it provides smoothness of bass and midbass, even into the lower midrange. Adding subs doesn't just give you impact for movies - this is for hifi too. Bass notes are more balanced from note to note, cello and male vocalists are given warmth and depth. Nothing smoothes the modal range better, so this is something else to consider when budgeting upgrades to your sound system.