Build vs Buying for Software Development and Gameing

Hello, Looking to get help answering some questions for building vs buying for Software/Game Development and gaming. So I had this all wrote out before and it didn't work so lets try this again. I will be going to school here in the next month for software development. I wanna get a computer that will be relatively upgrade free for a year or two since that's how long I will be in school and with a family its hard to get extra cash. Be able to play the newest/newer games in that time frame. Be able to run multiple programs at once and switch between them relatively quickly. And doesn't suck power like water. I've looked at Alienware and Origin, and gotten an idea about what they offer. Then thought about looking into building my own. Also I wont be doing much fps online maybe some strategy or something like that online cause I have satellite internet and fps online is like trying to race at the indy 500 with a grand am.... I also wont be doing much movie streaming as that will eat up my bandwidth (if any of that matters). I would like to get around a 23 in monitor or slightly smaller cause I read that its better to have a bigger monitor if your doing any kind of development so that its easier to switch or have multiple windows open at once. So those are my requirements, maybe impossible but Im not sure. So as far as the specs I was thinking, at least an i5 would like an i7 (why not exactly sure but I thought I read they are newer and its got better architecture for the multiple cores), at least 8 preferably 16gb ram ( i read that you only need 8 for gaming but with doing game development and running multiple programs at once the more ram the better), 1tb hd so I wont have to ever worry about running out of room haha, and then as far as graphics cards go that's where Im really wondering. I wont think I would need much in the department for the development aspect but for gaming I know its better to spend a little extra. I was thinking I just read an article on here about the different prices vs performance for the different cards, and I thought I saw the gtx 770 was a good card for the money being newer and faster I wouldn't have to worry about upgrading that for awhile. Another question I had about this area is most of the gtx cards and graphics cards out there have say 1 gb-4 gb onboard. Now does more = better or is it pretty much a number. The way I understood it was like ram the more you have the quicker it is for the card to process. Maybe Im wrong. Im not sure that's why Im asking. Now here is the kicker, I think im gonna max my budget out at around $2000. Could be more could be less. That's why Im not sure I could build something like this compared to what I could possibly get from the name brands. Thank you all for you help, and guidance.