I've gone the other way, I used to build all my machines from scratch - but I got tired of it and now go with emachines and a custom videocard and I'm much happier now.
Exactly. EMachines and Dell and HP machines are so cheap now that you can't build it yourself for less, or even the same. So you might just as well do what you do, providing the machine you pick has a decent motherboard and PSU in it, of course.