Originally Posted by Zon2020
But the point is that at idle and under light loads like watching video (and in contrast to previous generations of processors where quad cores were generally power hogging heat monsters) these new chips use almost the identical amount of power even though they represent a vast range of processing power.
So, for an HTPC, it's doubtful that you pay any significant penalty in terms of heat/cooling/noise to use an i5 rather than an i3 because for most of what you would be doing they're going to use about the same power. And for those few processing power intensive HTPC tasks like encoding, you'll obviously get the job done quicker (although then you will be using more wattage and generating more heat).
If CoreTemp's readings for CPU wattage draw are to be believed, my i3-2100T draws 4.0w at idle. The i7-2600k draws 5.4w at idle. 5.4/4.0 = 1.35, so the i7 draws 35% more, and likely has 35% more heat to dissipate at idle. I didn't do any tests of other common HTPC tasks. Sure, overall system heat/power use is largely unaffected when you consider an entire system will be drawing ~40w at the wall. But just talking CPU use and the ability to cool it, if you're trying to build a silent system (especially in a cramped case/cramped a/v rack), you might as well purchase only the CPU horsepower you need even if it is less than you can afford.
On top of that, the title of this thread is "Cheapest ever HTPC..." so it seems rather contradictory to suggest buying more CPU than you need considering the additional cost ("Cheap" part of the thread title) and extra effort/noise ("HTPC" part of the thread title -- as HTPCs are often synonymous with quiet) for cooling.
On the other hand, this thread has opened my eyes to the possibility of later moving my i7 to my server which runs 24x7. Given that the overall power usage at idle would be insignificantly higher even for 24x7 use, and given that the environment where it runs there are no noise/heat concerns, it is not unreasonable to do an upgrade should my requirements for my server change to include on-the-fly trans-coding of video content.
But yes, your point is well taken. These new chips are amazing in their efficiency. Imagine what Haswell will bring us...