This thread is a great idea, though honestly you have to update the OP over time for it to really work well.
Also, to me there's some huge gaps in the discussion around how people are going to use the system. Maybe you're assuming that since we're talking about HT, people are going to use it mostly or exclusively for HT (and games or similar stuff). And from people's posts, that may well be the case.
But to me there ought to be a big footnote that says, if you're going to listen to music as much or more - you have to take that into account for what you buy.
Ideally people might comment on which systems might be better for HT, music, or a mix. Eg from what I've heard and read, the Velodyne Front Rows are a good bet for HT, a bit less so for music.
And maybe nobody who comes here fits in this category - but If you listen to music mostly, you might do better spending your speaker budget on 2-3 speakers, depending on whether you listen to enough HT to want a center. Hook up two really cheap speakers in the back if you want to. Or not - not that much comes out of the surrounds, anyway.
Whether you get a sub depends on the speakers, your budget and your tastes.
Finally, it's worth mentioning used speakers. If the reason you're considering HTIB is to save budget, not time - you can find some amazing speakers used for not a lot of money. It does take time, but if that's the kind of thing you enjoy doing you can learn a lot, and end up with better speakers than all your friends, probably, too. If you have enough space, you can buy killer used floorstanders for not a lot of money on craigslist, etc, these days as people replace them with smaller speakers. And if you're willing to spend the time, and enjoy looking, you can find great bookshelves, too. I've seen older high quality speakers for $100-200 a pair.