I think the audio system has to be capable of reproducing quality sound first, and the most important part of the audio system, or the part that makes the most difference, is the speakers. If you can hear the system, or at least the speakers, on a demonstration and they sound good, then you know they at least have the potential to sound good if you set up your room correctly, or at least similar acoustically to the demonstration room. This may or may not include acoustic treatments, so I don’t see how acoustic treatments would be the first (most) important thing.
I would guess a majority of Audioholics (and certainly the general public) don’t have acoustic treatments per say (i.e. they may use bookcases, drapes, overstuffed furniture, etc.), although they may still benefit by their use. It would be interesting for the forum to conduct a poll of how much Audioholics spent (and separately plan to spend) on acoustic treatments for their audio setup. This could be done like the poll on how much Audioholics spent on their systems.
I think the room acoustic treatments for a multipurpose room (like a great room, family room or living room) would have a harder time with the WAF than the equipment itself. The wife would probably not approve of a multipurpose room looking like an anechoic chamber, as some vendors recommend. You are crossing the boundary between equipment and décor and that typically is the wife’s turf. If you have a dedicated home theater, then you probably have the say on what goes in it including acoustic treatments, but again I don’t think the majority of Audioholics or general public have dedicated (single purpose) HT rooms. (That’s another poll). So if you don’t get good speakers, you probably are not going to get room treatments as your first priority. It is the audio system, or speakers, first priority, then maybe room acoustic treatments as a second priority if you room needs them.