On the contrary to your contrary: the kind of person who builds their PC is the kind who customizes how it works when they're using it. There's no automatic assumption that they also harbor green feelings and want lower power consumption for idle/sleep.
Hell, many are proud of their beefy 1kW+ power supplies and the ridiculous power load they draw.
Others are proud of their energy-destroying bit-coin mining setups.
You certainly can't assume that the home builder cares at all about power consumption.
That CPU won't be appreciably more power efficient than a standard i7-3770. It just constrains its clock speeds in order to stay within a lower power ceiling.
TDP is all about cooling capacity and PSU capabilities. If you're worried about saving energy, get the processor that will run at the highest speed while computing so that it can get back into power-saving mode sooner. And you can always under-clock the standard desktop CPUs if you really want to - a 3770 can be configured to behave pretty much like a 3770T by tweaking the base and Turbo multipliers.
Fair enough. On the other hand segments of the market who think of the computer as a blackbox that is a bicycle for the mind are even less likely to care about any individual specification. Most people I know who build their own PC's are trying to optimize for some spec that manufacturers dont usually care about - loudness, gpu performance, low power draw, size, aesthetics.
On the other hand, you can't automatically assume they don't care about it at all.
I build most of my desktops, and I certainly want to reduce power usage when I'm not using them. Enough so that I'd pay for a power supply that supports the lower power states.
Not everybody who builds their own PC is doing so to make a ridiculously over powered system.
I agree. It really depends on why someone is building the PC. Sometimes you want to optimize the gaming performance, or video editing performance, or the file transfer speed and lower latency for a NAS box, or other times you're looking to optimize video playback, low power consumption, and low noise on an HTPC. All of those could be built by ones self, and each will usually require certain choices and trade-offs to achieve the desired goals.
Hell, many are proud of their beefy 1kW+ power supplies and the ridiculous power load they draw.
Others are proud of their energy-destroying bit-coin mining setups.
You certainly can't assume that the home builder cares at all about power consumption.