It never fails for me to post anything about a Dell, prove that it is a decent budget system (decent in terms of what you get for the price), and yet have at least one built-it-yourself zealot post that I'm way off . . . but then fail to back it up.
You want to back up that a build-it-yourself system is better than the $500 Dell box?
Then do this -- post the parts, links, and prices for:
i5-4460 or better
a motherboard
a power supply
a case
a kb
a mouse
a DVD+/-RW
a hard disk
4 GB of RAM or better
Windows pro (7 or 8)
Why? Because that's what's in the $500 Dell.
Do the above, and I will say, "OK, well done. You are right." Until then, I am doubtful that anyone will do anything other than tie the Dell, and then it will require mail-in rebates (which in my experience about half the time don't pay you back).