All Very valid Points,...In a black and white world ... if bucks are the main issue you buy what you can afford, ... if bucks are not an issue, you buy what you want!
But what about the shades of grey of cost verses price !!! If you go the 2500, it'll do everything the 2600 will do, just not as quick, that's the price you pay. With the 2600 it'll do everything the i5 can do and a tad quicker....over the next couple of years multi threaded apps will hit there stride, more cores will be more beneficial then raw speed, yes, eventually even in games!....and yes! at the moment it depends what you use it for, "At The Moment". We have so much choice right now that one can quite cost effectively buy chip specific.......... hardware to suit the type of application your going to play with and will do the job close or just as well as a chip twice the price. but hear is the cost effective catch,...if you buy the pricier option it will do everything better/faster/quicker.
I remember when dual core hit the market......Wow, two cores on one die! everybody did a double take because we had a 2.4Ghz (Dual core) out performing a 3.6Ghz single core by a belting big margin. (yeh right, maybe not in games you say)....Huh! people were saying how can this be, Intel and AMD have been telling us for years it's all about raw speed!
I still have mates who swear by there single core game Riggs (very old big kids) but if you want to play a game,run a virus scan while downloading a movie, ... a few more cores helps. Half a decade ago to even ask a question like this would have seemed bazaar.......Mmmmmmmmmmmm should I buy "A" with one core or"B" with 8 cores, Mmmmmmmmmmmmmm!...........Bit of a no brainer for me, ... Sell the dog , shoot the cat...... claim the insurance ... buy the i7
Aussie Allan