In the same bench you get your numbers from this happens:
*Omitted*
3.6Ghz FX8150 is 1.42, a 3.8Ghz FX8150 is 1.48. See the problem again?
iTunes isn't a single thread benchmark. It gains from 2 cores pretty well. It looks like the intermediate Turbo for the 5400K and 5800K are 4.0GHz and 3.7GHz respectively.
The 3.6GHz FX-8150 has TurboCore enabled so it should run at 3.9GHz, while the 3.8GHz one has fixed 3.8GHz frequency. It may briefly be able to reach higher frequencies as well.
About the FX-8350: The actual frequency gains are pretty minimal.
http://hardforum.com/showthread.php?p=1038899527
FX-8350 - 4.0 GHz base speed, 4.2 GHz Turbo
FX-6300 - 3.8 GHz base speed, 4.1 GHz Turbo
FX-4320 - 4.2 GHz base speed, 4.3 GHz Turbo
Let's compare that to the previous generation:
FX-8150 - 3.6 GHz base speed, 4.2 GHz Turbo*
FX-6200 - 3.8 GHz base speed, 4.1 GHz Turbo - Identical
FX-4170 - 4.2 GHz base speed, 4.3 GHz Turbo - Identical
While the base frequencies are noticeably higher on the FX-8350, the FX-8150 supports all core Turbo running at 3.9GHz. Looking at how the lower end chips aren't clocking higher than the predecessors, the multi-core frequency might end up being at base 4GHz, or slightly higher at 4.1GHz. That's 2-5% higher frequency.