I just installed that very MSI card in my system today. It's a great card and silent at idle(just swapped a passive 6850 for it, I don't notice any extra noise) but it doesn't overclock well. It won't go past 1075mhz which is a pretty low OC for the 7770s and has no voltage tweaking. Put the extra money into one of the long 7770s with a beefy cooler if you love tweaking or pick up a used card from one of the last gens. for gaming I wouldn't go lower than a 5770 in the 5 series, a 6770(rebrand) in the 6 series, or a 7770 in the 7s. You also may want to tell us what res your friend is running. A 6870/5870 will pretty much max out anything at 1680x1050 except a few AAA games. Even with the 5770 I had a few years back I could play Crysis near maxed out and have it still be playable. Ultra with 2xAA gave me a steady 20FPS, good enough but not ideal.
I'm not too sure what to recommend you CPU wise. The i3s from Intel don't OC, but they still hold up well against Bulldozer. I'm not sure how an OCed BD would compare however. You may just want to go with a Phenom II, they seem a good value these days and would be a good match for a 7770.
For motherboards, try and get an ECS or an MSI(Not if you go AMD!). I've had some really nasty support from Gigabyte and ASUS's CS actually went far enough to try and extort me for repair work, when I refused they ripped the CPU bracket near off of my board and sent it back. I've been running ECS ever since and everything has worked perfectly.
And take a look at some MATX cases, Fractal and NZXT have some really nice entry level cases that won't leave you with cut wrists and a nest of wires like most of the cheapies.
As for the drive, with the prices as high as they are don't go too crazy. Get your friend just what he needs, I bought a 1TB and I use maybe 250GB at max. And that's with about 10 games installed and 60GB of music.