Love my i5-2500k with my P67 UD4.
For the love of all that is holy, DO NOT GO WITH THE ASUS P8P67 PRO. It seems like ASUS really slacked on their P67 line and you are really rolling the dice getting a P67 from them. I hear good things about their Z68 line, so I'm thinking they just put more effort into that.
I went through not 1, but 2 P8P67 Pros before finally giving up. They look pretty, but are ridiculously unstable compared to their gigabyte counterparts.
First one, sound card just died after about 29 days of use (lucky me, could still return it to newegg within that time frame). Second one caused all sorts of windows instabilities where comp would just lock up in windows and then cut power to all usb ports. Would do it randomly too - sometimes it would only take 5 minutes before the comp locked up, other times it would be fine for 3 days first. Ugh. Had the double-boot issue on both of them as well (tried all the fixes proposed on the asus forums; none worked)
And both of them required higher voltages to overclock.
My P67 UD4 can reach 4.5 Ghz and still be under 1.3V. Both the ASUS P8P67s I owned could only reach 3.8 before breaching the 1.3V barrier. If I wanted to get to 4.5 Ghz, I was looking at upwards of 1.37V.
So basically if I'd stayed with my ASUS P8P67's, I would have cost myself 700 mhz of performance. 😵
Seems like Gigabyte has problems with their Z68 line acting up though. So I guess the tl;dr version of this would be:
If you're going P67, go gigabyte
If you're going Z68, go ASUS.
Either way though, the i5-2500k should serve your brother well. 🙂 I've been running mine basically 24/7 doing things like folding and keeping the CPU at 100% utilization since February at 4.5 Ghz. Still running strong.