4k on a GTX 770 isn't realistic. Either buy a lower res monitor, or beef up your card. A 770 is a 1080p card, it can also get it's feet wet in 1440p. I'd personally rather go with a 1440p 144hz panel than a 4k one.
Nothing will last forever. Everything will go out of date. An I5 will go out of date just as fast as an I7, since there is no difference between them in gaming performance. An I5 should last you a good 6 years. Your dad is very mistaken.