Should i buy a used i5-2500k?

It may be very legit but then you don't know how it was used. Did the original owner OC it heavily? then sell it cause he may have know he beat the $#@# out of it? yes your friend has it and it turns up fine...for now...but how long will it last? At least with a new CPU you can return it if it dies...with "second hand"...your on your own! Buying anything "second hand" is always chancey.

I5 2500k Buy

well the difference is not drastic so i'd probably go for a new one and if you wanna buy just because it's already unlocked then don't bother...in order to do that you wouldn't need to walk on fire or anything it's simple...

but at the end of the day a new product from a store has warranty and everything else

so new would be a better option unless you're on a budget

Go for it. Tbh If you keep doubting yourself instead of getting something your never gonna be buying something. Theres always gonna be something better :D It is the latest processor and will last a few years. Especially with overclocking. There ARE benchmarks already.

Often people overclock them and kill them but it might be a good idea if you know what this guys rep is like.

On ebay you will be able to find out real quick if he is bodged.

get a core i7 3770k