The right iMac

My girlfriend and her family, thanks to my insightful advices, after getting two iPhones 4 and an iPad, are finally (almost) ready to leave behind their "not-so-working" pc and buy and iMac.

Problem is, they don't know which one to get. All right, they won't buy the 27", it way too big, but they aren't sure which 21,5" configuration to get; for their needs I told them to get the entry level one, it will be more than enough.

Notwithstanding my advice they were thinking of getting the 2,7Ghz model with 1TB hard drive, also adding 8GB of Ram. My question is, do they really need it? (No, they don't). In terms of speed and normal usage what will be the difference between the entry level model and this model? If it was your choice, would you add 8GB Ram (instead of 4GB) or the i7 processor?

Plus:

What day is black friday?

 

Sorry for my not-so-good english!