I5-2500k vs. i7-2600k URGENT

Hey all,

I have purchased an i5-2500k for $165 and have the opportunity to purchase an i7-2600k for $190 (or $200 if the bonus 10% does not work) + 8.5% tax.

This is my current build so far, with a budget of no more than $700 (closer to $650 if possible).

Processor: Intel i5-2500k. $164.99
Mobo: Gigabyte GA-Z68XP-D3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX. $15.99
Hard Drive: Samsung 830, 128GB SSD. $140
Optical Drive: Don't think I need one
PSU:
Aftermarket cooler: CM 212 $23
Video Card: No idea yet. Will wait till mid May to buy to get lowest price (maybe 6870 or 7850 depending on price? Maybe something in that range for nVidia??)
Case: HAF 912. $35 AR
Wireless: will not purchase
RAM: MEM 4Gx2|CORSAIR CMX8GX3M2A1333C9. $25 AR

I intend on keeping this computer for 3-5 years, with video card upgrades. Is it worth me attempting to privately sell my i5-2500k (eg. Craigslist; maybe around $190) in order to buy the i7? I cannot return the i5 because then I will lose the combo discount that I received for buying the mobo at the same time.

I will be using the computer for games, web browsing, movies, that kind of thing.

I intend on playing games like HoN/Dota 2, SC2, Call of Duty, CounterStrike: GO (whenever it comes out). So basically, MOBAs and FPS. I don't intend on playing games like Skyrim or other RPGs.

Will I see a significant boost in performance with the i7 long term for gaming purposes? I don't do video editing or photo editing, but I may be doing scanning/rendering in terms of PDF files (eg. I take pics with my phones, upload to computer, then use a computer program to convert jpegs into PDF files). Again, waiting an extra minute is not a big deal, but IF games down the road (eg. in 2 years or so) may require more cores, perhaps the i7 is better?

This is urgent because I will only have this Saturday morning to acquire the i7 processor. It is currently 1240am Friday local time, which gives me about 36 hours till purchase.