despite of lack of L3 cache seems that 2500K performs exactly like 2600K in all single thread benchmarks.
give a look at these 2 links:
3dmark 03 and 05:
http://www.overclockzone.com/zolkorn...ge/index11.htm
super-pi 32M:
http://www.hardwarecanucks.com/forum...-review-9.html
super-pi 32M efficiency:
2600K || 3800 * 563,408 =2140950,4
2500K || 3700 * 570,663 = 2111453,1
2500K seems a pretty good deal if you are looking for single thread benchmarks.
sorry if link from other sites aren't allowed but i don't have in my hand these new cpus, so i've no way to make a comparison...

would be great if someone that have both cpus can make a comparison for us waffling guys