Alright, this is an interesting one. For starters, I have to say that I am impressed with the quality of this computer for the price Dell is offering; starting at $750. If you're looking for a prebuilt, this is probably a good one to go with. For starters, it comes with the email@example.com GHz, but you can choose the firstname.lastname@example.org GHz. It's a $150 price difference, but I feel that the one included in the price should be able to handle most GPU support processes without any problem. Of course, if you need more that I am not aware of, the i7 is definitely an upgrade, but depending on your budget, it may or may not be worth it.
It comes included with 8 GB of DDR3 RAM@1600 MHz, so apparently Dell has stepped up the game by providing 1600 speed as their new standard... who knows. Anyways, for most games, such as Battlefield 3, Skyrim, etc. RAM doesn't really make that big of a difference, but for video editing, multitasking, more RAM isn't really a barrier. Again, you can double that amount with $150, but you can also go in between with $75. I really think if you need any upgrade at all, 12 GB would be fine because that is already pretty much at the high end of the consumer grade computer RAM.
To begin with, the GT 640 and AMD 7570 are both low end cards from both companies. Remember that even though they are the new generation of GPU's, the AMD 75** are supposed to be an improvement on the 65**, and are not supposed to compete with the cards such as the 6950, 6970, 6770, etc. I'm pretty sure that this is the same for the Nvidia Cards. Honestly, it depends what kind of games you will be playing, because even though the cards are low end, they CAN handle most modern games at decent frame rates, maybe around 40-50 max. However, if you are looking for longevity (relatively) and improved performance, the additional $150 towards the 7770 would definitely be a vast improvement with another gigabyte of video memory. Otherwise, I would either stick with what it comes with. End price should be around $1000, but I'm not sure what your budget is!!
If you want 16 GB RAM, configure it with 8, buy a 8GB kit yourself, and RAM installation is really easy, open up the case, stick the 2 units in, close it and BAM 16 GB. I have one on order with the GT 640. You could email them directly about taking some money off and get it without the video card and use the saved money to buy one yourself. If you aren't a system builder or don't like to get inside a computer, you would need the HD7770 if you are going to do some hardcore 1080p or plus video editing. It will also be pretty good with gaming, considering it also has 2GB GDDR5. The 12GB setup they have is 4+2+4+2, which isn't the best, but doable.
I ordered the XPS 8500 with the i7, 16gb, HD7770, Win7 Pro and have been very happy in general - but there is a fly in the ointment here.
A good number of folks are reporting in Dell forums that their PCIe 1x eSata cards will not be recognized in the device manager. We have checked our cards on other Dell Win7 pro machines, and they are recognized - work just fine. Other cards work fine in the PCIe 1x slots. Dell is aware of the problem, and have requested service tags from folks who have reported it, but so far no solution.
One person has also reported a PCIe 1x TV tuner card exhibiting the same problem.
Other than that, this machine rocks. Hope they find a solution soon!
I agree I wouldn't buy any Dell computer. As schmuckley said you can build a much better computer for around the same price and not have to deal with Dell's junky internals taking a dump on you the day after the warranty is up.
There are people who would say it's just "cool to bash Dell" but Dell being notoriously crappy isn't just a theory. As an 8-year Dell owner (whom is a competent PC user), I can certainly say stay away from Dell. Avoid it like the plague.