The problem SB-E will face on desktop market is that not many applications will utilize that many cores/threads.So what if SB-E comes just 10-15% on top of Westmere 6C? That would also mean it will be 15-20% faster than 2600K. Is that a failure in itself then? What if top model Zambezi 8C is just 10-20% slower than 6C SB-E while costing 3x less?
Also in well threaded code I think 8C Zambezi will really shine ,so it won't be one trick pony(high Turbo core).