"amuffin" is right, but if your notebook has switchable graphics (means that you can turn off the dedicated GPU while in "power saver" mode), you wouldn't have to worry much about battery life.
You shouldn't buy an I7 for gaming since it hyperthreads (divide real cores into two virtual cores), while games only use mostly 2 threads (cores), you would be actually using only two "virtual cores" that ends up being only one "real" core.
(1/2 + 1/2 = 1)
Also, the I5 and the I7 are basically the same Chip, and Intel just disables Hyperthreading for the I5. It tends to confuse people thinking that an I7 is better than an I5.
This is why many gaming systems use an I5.
16 GB of RAM is Largely unnecessary (as for 2012), except if you want a large amount of ram to work in extreme multi-tasking (800 Google Chrome Tabs, 6 1080p Videos, 4 MS Word, 9 Photoshop and 12 Adobe Readers all open at the same time) or to be future-proof, but your other components would be deprecated by then.
Hope it helps!