from the fx8150 reviews i've read,
4.4-4.5 on avg. on air, typically 4.4 ghz.
using water cooling it goes higher.
4.5-4.8-.9, sometime 5+ (2 reviews iirc), typically 4.5-4.6 ghz.
fx8150's max turbo core speed is 4.2 ghz iirc so the oc speeds are not that much.
even on those speeds fx 8150 was slower or nearly at par with 2600k oc'ed @ 4.6 ghz, sucked up a LOT of watts. 2500k on 4.4-4.6 ghz could keep up with the oc'ed fx8150. 2600k's max turbo boost speed is 3.8 ghz on single core and 2500k's is 3.7 ghz iirc.
imho amd's ghz and cpu cpec numbers are sorta deceptive compared to intel's. they always look more from a spec perspective but they always end up being slower in tests/benches.