As far as I know, an i7 would be a waste of your money if all you're doing is what you outlined. And, regardless of whether you opt for an i3 , i5 or i7, get as much RAM as you can afford, or that the PC can take.
I have an i3 for the last 12 months. Genral day to day use, some Office applications, internet and lot of video and photo editing...i3 is very good. No probs since purchasing. Hard drive went 2 weeks ago but new one installed and was informed this was an issue that had cropped up with some Toshiba laptops. Luckily I back up every week so nothing lost. i3 all the way.