Wow, very nice writeup!
I've been building my boxes for a long time, and firmly believe it is the way to go for the hobbiest and/or gamer. Being able to pick parts and later upgrade as needed is wonderful.
One thing, there are lots of sites with constantly updated articles about what parts currently make sense for a given computer requirement. I like
Ars Technica Guides
they do various types of build recommendations. The Hot Rod is good for gamers.
(No affiliation, other than as a a long term reader).