The Intel Core i5 3470 is a nice performer that's generally right in front of the Core i5 2500K "Sandy Bridge" processor. The more expensive Intel Core i7 3770K definitely packs a much greater punch when the workload is able to take advantage of eight CPU threads and slightly larger Smart Cache (6MB vs. 8MB) plus its obvious higher clock speeds. The i7-3770K also offers much better integrated graphics as shown in the HD 2500 Linux review. Now let's look at the performance-per-Watt and thermal performance for these four Intel processors in a couple of the Linux CPU benchmarks.
Beginning with the very CPU intensive C-Ray, the i5-3470 at its stock frequencies was running at around 70°C with the Intel reference HSF. This temperature is right in line with the i7-3770K but these Ivy Bridge CPUs are warmer than the previous-generation Sandy Bridge parts.
The full system AC power load -- as measured via a WattsUp USB-based power meter that was automatically polled via the Phoronix Test Suite -- was at 88 Watts while running C-Ray. The i7-3770K meanwhile was at 99 Watts, the i5-2500K at 106 Watts, and the i5-2400S at 79 Watts.
Now when looking at the performance-per-Watt of these CPUs with C-Ray by having the Phoronix Test Suite take the raw C-Ray result over the average system power consumption, we see the i5-2500K delivers slightly better performance over the i5-3470. The i7-3770K meanwhile delivered the best performance-per-Watt for this multi-threaded test. At least the performance-per-Watt of the i5-3470 was well ahead of the previous-generation i5-2400S.