For those who build their own or are thinking about it, I suggest
Logical Increments, a site with tested builds and parts lists at every price level. Part picker is good too for finding things that work together.
I still build my own and continue to upgrade them until the form factor of the motherboard and/or the component connectors are obsolete. I buy excellent mid-tower or full-tower cases that have room for multiple hard drives and large, modular power supplies.