You'd have to overclock using the BCLK. However, I highly recommend not doing this as it causes a LOT of stress on the motherboard. Using the BCLK to overclock causes stress on the RAM, PCI-Express, And just about everything else on the motherboard. The last couple generations of motherboards just don't take kindly to overclocking the BCLK. And the gains aren't going to be that impressive in real world.
100 x 33 = stock 3.3Ghz
110 x 33 = 3.630Ghz
And 110 on most P67/Z68/Z77 motherboards is hard to get to stable. The K series is there mainly for overclocking purposes, the non-K; it's best to remain stock with them.
However, the turbo technology is designed to keep the processor within stock TDP limits. So the processor cannot effectively go over the 95W rating. At 3.6Ghz with all four cores operational it can pass the TDP. So even setting the turbo that way is ineffective once the TDP is calculated by the processor.
Using the multiplier and or BCLK can bypass the limitations as it's not being effected by the Turbo and for the most part completely disables the turbo ability. Turbo simply increases the efficiency of the processor in low number of threads. Basically shutting cores down to bring the processor to a higher speed without crossing that TDP line. Effectively at max turbo the i5-2500 is a 3.7Ghz Single core processor that is good for single thread applications. However I haven't seen any applications in the last few years that didn't benefit from at least a dual core.