http://pcpartpicker.com/p/rj0O
This is what I came up with, used an i5 processor as going with i7 won't really net you any real performance increase. And I have a radeon 7950 in there along with 16gb ram. I threw in a cheap heatsink just to give the heatsink a proper airflow direction so it doesn't circulate the heat back into the case like the stock ones do.
The case isn't flashy or anything but you need to buy more fans for it, you can go the cheap route and just pick up a bunch of low decibal low cfm fans, which is what I would do. There's a 4 pack of cooler master fans on amazon and probably a few other places for around $10 but be warned they use 3pin connection so it may cause some headaches. I personally would go that route and wire them up to a cheap fan controller and since their already low cfm/decibal fans try to fine tune it so it's completely silent. Or buy a bunch of cheap low cfm/decival fans which use a molex connector and hook it up the PSU as I believe the 3pin fans hook up to the motherboard if I am not mistaken or a fan controller if it supports that and i doubt the motherboard will support all these fans. Fans will set you back probably 15-20, but give you airflow that is only rivaled by much higher end/expensive cases. Oh and Newegg also gives you more details on how many fans this case can hold.
You can also squeeze in a 7970 in there if you want if your willing to stretch your budget a few dollars and look at the budget after rebates. $915 after 50 mail in. I go this route if you can.
http://pcpartpicker.com/parts/partlist/
Oh and it says theres a chance there is a compatability problem for the motherboard, there isn't according to reviews on newegg. According to them it support Ivy Bridge right out of the box so you should be set.
If you wanted to cut out $30 out of the build you can drop down to 8gb ram which is more than enough for gaming and still keep ddr3 1600 cas 9 ram in it and you won't notice a performance hit.
I put in Windows 8 in the build you can easily swap it out for 7 if you want without paying more as I think it was the same price.
Forgot to put in an optical drive, so toss in another $15-20 for dvd burner or $50-60 for blu-ray burner.
Closest thing dell has in terms of performance for gaming seems to cost close to 2k in comparison to the 7970 build from a quick glance, just another thing to think about if your still on the edge about building your own. And I just took a look at the Dell model you were looking at, even if you got the highest end GPU they have for that it won't even be close to what you can get from building it yourself, so I highly recommend not buying that Dell if you actually want to do any gaming.
And lastly this is the more budgeted approach which has 8gb ram, no aftermarket heatsink, and the dvd burner. It just needs additional case fans. (Yes I am bored and I like driving away customers from dell after they screwed me over so many times. Thus is why this post is so long and I probably edited this about 10x now) Come out to $885 after $40 mail in.
http://pcpartpicker.com/p/rj8l