I have built my own pc's for several years now. I find it best suits my needs to compile my own specs on the hardware of the pc. If you buy one from a shop it tends to be missing one or several of the specs you want the pc for, which then defeats the object of me getting it.
I haven't built a new one for around 2 years now. I may just upgrade my current one when I get the chance and some spare cash. But even as it is a few years old, it still suits most of my needs without any issues. It's currently a 4Gb ram, i3, I can't remember the exact specs. I'll try to dig up the old list I have of it! Although I have a graphics card that keeps breaking on me. Since I've had it I've had to send it back 3 times now.