Jason, very fair comments. First of all, when you say that HT speaker quality is not as critical to the overall system compared with "pure" music-listening, that really crystallizes my own listening experience. The HT is looking to create an ambience more than anything else, sound source is usually quite low quality compared with a high quality music recording, the emphasis on special effects requires very different speaker qualities compared with "pure" music.

As far as your feared "rope to hang yourself", the criticality of phasing and stage (among other things) in "pure" music lstening I think is EXACTLY why music requires higher-quality speakers than HT. It is ALSO why I have never heard a multi-channel system, even in the high-end stereo shops, that competes with a high-end conventional stereo set-up for sheer quality / experience of music reproduction. I love your phrase "paint the soundstage": that is exactly what a good stereo pair does, even with my eyes open I "see" the musicians in my mind's eye as I listen to the speakers. I purchased a Zalytron MTM kit for my center channel (is not used for music listening) that is technically high quality for what it does but would never "paint the soundstage".

But most of those HT systems I've experienced, both at friends / neighbors and in shops, have "sweet spots" that are little or even no larger than those of a fine stero system.

Regarding your 90%/50% I have more to say. In particular, the only real way to achieve this kind of ratio is to build the cabinets yourself. Doesn't require extensive skills to build solid, straight-forward cabinets, but DOES require extensive skills to build ones that, at my age, I would find aesthetically acceptable. (Aside: I'm staggered by the prices of some speakers that have vinyl wrap as their finish, well I guess at least they aren't plastic cabinets). And I would still say that most kits, even in the $1K range, have only mediocre crossovers: if you can point me to exceptions other than North Creek (see below) I'd love to know. These remarks based on an ongoing extensive search for what I intend to be my "final" main-speaker set.

Speaking of my search, North Creek and Tyler Acoustic (not a kit by the way) are both interesting "factory-direct" choices that I have researched extensively and actually to me appear to be the quintessential approaches of highly engineered (North Creek) 2-way system versus solid engineering with a lot of your money put directly into a relatively large number of drivers (Tyler). Perhaps best for a different thread, but my wariness with these direct-only systems (including others I've considered) is inability to pre-test, and the fact that all their purchasers love it is frankly not helpful: seems to me that everybody who spends that much on speakers loves them!

Steves: perhaps you are right to emphasize the last 10%, but it seems to me that most people who post here are by definition into the last 10%.

Lena: I totally disagree with your statement on cabinets. Material used, thickness, bracing, porting or line transmission, stuffing, etc.: the cabinet design and quality is a CRITICAL CRITICAL ingredient of the overall result.

Understood… I was referring more to the ‘construction’ as in crafted for fit and finish at a cabinetmaker’s level of expertise, (he was one) that was what my “beautiful women” remark was illustrating. He has the skill to make me an exact duplicate of the ‘Temptation’ cabinets’ external facade. Our sole position of strength in starting a project like this would be our ability to handle (from Jason)‘veneers or fancy cosmetics’. I’ve seen many DIY speaker builders state a need for kit resources with high quality finished cabinetry for their projects that being the lack they have in DIY their talent (and interest) lies more to the electronic side of speaker fabrication.
The engineering behind cabinet ‘design’ as it directly impacts sound output I have noted has many variables. Enclosed/ported/blockable ports/locations of ports to relation to cones/baffles/Chamber sizing as it relates to air volume requirements, damping/ resonance/ etc. The ‘shell’ is the only expertise we have (thereby my ‘easy’ comment), how many of us have complained that many producers of AV products would be better served at times by putting more of their CPU into components over looks.
Amongst all the impact interactions of a DIY I think it’s the crossovers that appear to be one of the most intimidating aspects.