double_d1 :
I do a lot of video transcoding, squeezing long movies on to DVD disc. It uses both cores to the max.
That would definitely be helped by a new core i5, but they also have the new Quicksync feature which speeds up video encoding/decoding tremendously for programs coded for it that would make you have to get a H67 board. This would disable the overclocking ability of the unlocked processor, though, I believe the lower models also have Quicksync in them as well, so they would be a cheaper alternative once more programs use the fixed function hardware.
I would wait for the Z67 chipset that should be coming out soon, since you've already waited so long. The Z67 chipset should allow you to overclock and use the graphics core(where QS is located)
BTW, QS supposedly made a minute of video encoding(even with video cards) into 10-20 seconds. Another was only slightly faster, but it still beat out the other cards.
http://www.tomshardware.com/reviews/sandy-bridge-core-i7-2600k-core-i5-2500k,2833-17.html
This shows about a 2x speedup when compared to other cards though:
http://www.anandtech.com/show/4083/the-sandy-bridge-review-intel-core-i7-2600k-i5-2500k-core-i3-2100-tested/9#
Once QS is used in more software, this would be perfect for your use. Even now, the 2500k is a fast processor that can handle encoding blazingly fast, especially if you overclock.