I'm going to assume by IPS you meant IPC in which case you are wrong because SB-E has slightly higher IPC than SB (more cache, more memory bandwidth; it helps a little, but not a lot) Also, the 3930K is something like twice as fast as the 2500K in highly threaded work. This build is intended for a professional envirnment, or at least for professional work. It should be able to get great gaming performance without sacrificing the more important productivity performance and that it has excelled at. My only complaint is that it has a single 7970 instead of dual 7870s or 7950s and that complaint is nullified by AMD's GCN Crossfire driver situation, so there's little that Tom's could have done anyway and it's not their fault.
Also, the 3930K in this system is overclocked just as far as a 2500K would be, so frequency is another null point. You're a failure at being a gamer just as much as reading the article to know the whole point of this machine. Considering the many times that people with the same stupid ponit of view as you have been told why this is as it is, you should be ashamed of your self for spouting your stupidity instead of learning from the stupid mistakes that so many other commenters made.
The 7970 is a great compute card that puts all other consumer cards to shame. Considering the price of high performing professional cards, it's an excellent option for non-gaming work. STFU and GTFO if you can't see past your ignorance; perhaps it's your head that should be checked.
Also, I'm getting kind of sick of seeing video cards being referred to as GPUs by people trying to sound smart. A video card is NOT a GPU and the 7970 is NOT a GPU; it's a video card. A GPU is a specific part of a video card. For example, the 7970 and 7950 have the Tahiti GPU. The 6950 and the 6970 have the Cayman GPU. The GTX 580 and 570 have the GF110 GPU. I could go on and so could a lot of other people here on the forums. "Video card" and "GPU" are not synonyms and they should not be considered as such. We certainly don't refer to the motherboard when it has a CPU and RAM on it as the CPU because the two are not the same; the CPU is part of the computer, so why do some people do it with video cards and GPUs?
SB-E i7s are obviously better than SB i7s for a productivity/performance machine if they have far more of the same architecture cores, far more cache, and far more memory bandwidth (granted, those last two probably don't make huge differences, but they do help). Tom's wanted a PC with more productivity performance so they chose a faster CPU. I don't see why it's a hard concept nor why you need someone else to reply to you and explain it after so many people have explained the same thing to other people.