That is a very good guide, the only thing I'd disagree with it about is
When I'm designing a PC for myself or for someone else I always start with the motherboard, that way everything is narrowed down for you, type of processor, type and size of memory, graphics cards and expansion cards. All the names they mention I tend to use, as it is the best of quality e.g. Asus Motherboards, Lite-on DVD drives, Seagate* Hard drives, Creative sound cards etc.
*Seagate now own Maxtor and as a result, have replaced the entire Maxtor range with Barracuda's so you can pick up what is essentially a Seagate hard drive at a Maxtor price.