The 2500k is completely different than the 920!
i5-2500k
Sandybridge architecture
4 cores/4 threads
i7-920
Bloomfield Architecutre
4core/ 8threads
Ivybridge is essentially the same as Sandybridge, but features slightly faster cores, better integrated graphics, less power consumption, and better on board graphics. It also has pcie 3.0 natively supported, however this does not do anything for current graphics cards. Unfortuenatly ivybridge runs much hotter than sandybridge, and offers only 3-5% overall performance increase.
BTW if you have the 920 then you should keep it and overclock! The 2500k won't outperform the 920 in multi-threaded applications.