If you are not gaming, the Intel Haswell graphics can work well for up to 4K resolution. No graphics card needed at all, saves $$ upfront and typically draws a lot less power than added graphics cards. I’m running a WQHD monitor (2560×1440) and a sidecar 1440×900 TV off an i7 Haswell system and it has no trouble with loads of pedestrian stuff running at the same time. I noticed I had a Dr. Who episode going in Netflix full screen on the small monitor, a YouTube about an electronics mod and some vid somebody posted on Facebook all running at the same time with no problem.
There is a similar AMD built-in graphics system available and these days I’d consider that. too. When I built my last box the AMD thing was new and was relatively power-hungry. These days, what I read says the AMD system is definitely competitive with Haswell.
(If you are gaming, of course you will want a rip-snortin’ graphics card or two. The cards out there are gorgeous bits of tech, I almost wish I needed one.)
I recommend a premium power supply. Most PS get pretty good efficiency in the higher load range (80–90%) but the better ones will have 90+ efficiency ratings all the way down to minimal loads, where most of our computers sit being idle most of the time.
Don’t get the cheapest motherboard you can find either. If you can shell out for it get a mobo that can be over-clocked, whether or not you ever intend to overclock it, because those are built to stand extra stresses and remain stable. At standard speeds they can be more durable than a lesser mobo.
I wouldn’t bother paying the premium for an overclock-capable CPU, though, unless you really, really want to do that. They just cost so much more than the near-fastest standard parts. I see great prices in the low-to-mid 3Ghz range, but several hundred more for the near-4Ghz parts.