Intel has improved the thermal dynamics of the IB line since the early release (I believe that they now use a better paste, but it is still not solder). While the SB processor can be better OCd, the IB is still competative at a reduced speed because of its 15% performance advantage over the SB. Simply put: if a SB 2500K is OCd to 4.6 GHz, it can do the same workload as the IB 3570K OCd to 4.0 GHz.
Redeemer may be a speed demon, but IB still rips the doors off the SB at the same clock speed.
& imomun a 4.5 GHz IB = a 5.175 GHz SB (not 4.7).