What stops you going for the 8150 other than price?
It doesn't represent good value for money and from what I've read so far, it has similar overclocking headroom to the 8120.
The 8120 is priced about right, performance wise per watt it's about on or edging the i2500k.
As both are unlocked you might as well save £40-50 and just adjust the multiplier on the 8120 to match the 8150.