Shadorne, my rooms have all worked without treatment, every place I've lived since 1969. My rooms tend to be carpeted and relatively stuffed with furniture and of relatively large size, so that mitigates my need to treat somewhat. However, the assumption that every room will need treatment does not jive with my personal experience.
My example earlier in this thread had a speaker investment around $1,000. At that price point you can find some very nice designs that use good, off-the-shelf drivers combined with good cabinet and crossover design. A top echelon $1000 speaker with good electronics will easily reveal weaknesses in the cables, ICs and the source.
I think it was on the Stereophile blog where I recently saw a survey of audiophiles. A very high percentage of those responding say that they have between $5000 and $10000 invested in their systems. That's enough money, like my proposed $5000 system, to put together a really revealing and musically satisfying rig. I think that spending $2500 on speakers for such a system and $100 on wire would be a mistake, yet many people would chose to do that.
Dave