Core i5 2500 has four cores and just as many threads

Eight threades reserved for i7 only
Core i7 2600 is the name that will mean you have eight thread support while Core i5 2500 is the runner up product that works at 3.3GHz, has 6MB of cache and 3.7GHz turbo overclocking. Core i5 2500K means that it is an overclocker friendly version, meaning unlocked, while the non K Core i5 2500K is a plain normal Core i5 Sandy Bridge.
The graphics runs at 850MHz and overclocks to 1100MHz. This is still slower than 1350MHz, which the highest clock on Core i7 CPUs.
The TDP of Core i5 2500 is 95W and you can expect them to launch in early 2011, Q1 2011 to be more precise.