mtmcool,
The i5 2500K is typically a great overclocker. Some have reached 5.0 at 1.35. The average overclock is at least 4.5 at about 1.35, so you're good.
Don't use IBT for thermal testing, use Prime95 v26.6 Small FFT's -
http://windows-downloads-center.blogspot.com/2011/04/prime95-266.html
You might want to read this:
Intel Temperature Guide -
http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html
From the Guide:
" ...
Overclocking and Vcore:
Overclocked processors can reach 130% to 150% of their TDP envelope (Thermal Design Power) when using either auto or manual Vcore settings, so high-end air or liquid cooling is critical. Every processor is unique in it's overclocking potential, voltage tolerance and thermal behavior.
Regardless, excessive Vcore and temperatures will result in accelerated "Electromigration" -
https://www.google.com/?gws_rd=ssl#q=Electromigration - which prematurely erodes the traces and junctions within the processor's layers and nano-circuits. This will eventually result in blue-screen crashes (BSOD), which will become increasingly frequent over time.
CPU's become more susceptible to Electromigration with each Die-shrink, so 22 Nanometer architecture is less tolerant of over-volting. Nevertheless, Vcore settings should not exceed the following:
-> Core 2
1st. Generation 65 Nanometer ... 1.50 Vcore
2nd Generation 45 Nanometer ... 1.40 Vcore
-> Core i
1st. Generation 45 Nanometer ... 1.40 Vcore
2nd Generation 32 Nanometer ...
1.35 Vcore
3rd Generation 22 Nanometer ... 1.30 Vcore
4th Generation 22 Nanometer ... 1.30 Vcore
When tweaking your processor near it's highest overclock, keep in mind that for an increase of 100 MHz, a corresponding increase of approximately 40 to 50 millivolts (0.040 to 0.050) is required. ... "
Hope this helps,
CT