Um.  Normally I don't recommend name brand machines.  In my experience, they are lower quality machines and proprietary (harder to upgrade and non-standard parts).  I have been building, servicing and upgrading ,machines since the late 80's.  Dells can be very proprietary.  I just got through upgrading one for my sister in law and it was not fun.  BTW are you planning on running a 64Bit OS?  If not, you will only be able to use just over half of that 6GB RAM you are getting.  All 32Bit OS' can only address a grand total of 4GB of memory, this Includes your video card memory and any virtual memory files that might be created by any software.  Since you are getting a 512MB video card, this means you can only access 3.5GB of RAM for main system memory.  Also you didn't mention Hard Drive Space.  Get as large a drive as you can afford.  Never ever ever bargain hunt for a PC.  There is no other product you can by that adheres more to the phrase "You get what you pay fore."  Oh, you should consider a custom clone machine with an AMD CPU.  They are usually less expensive than a name brand system with the same specs.  And always better built.  As an example, here is my system.

AMD Phenom X4 9600 Quad CoreCPU
MSI K9A2 Platuinum Motherboard (The most highly recommended motherboard for AMD CPUs.
4GB Corsair DDR2 RAM
ATI Radeon HD 3650
1TB in 2 Seagate 500GB Drives. (I also have another 500GB Drive I took out of my last machine, and another 500GB drive I just got for Xmas for a total of 2TB storage.  But only the first two drives were in it when I built it.  All drivbes are the newer faster SATA II interface type.  Avoid older IDE drives.  Dell usually uses these because they are cheaper, but much slower.  And never buy Western Digital drives.  With IDE Drives, the only way to get more than 4 hard drives in the machine is to add on another IDE controller card which is a hassle.  SATA II drive motherboards typically have between 6 and 10 SATA II interface jacks.
Soundblaster Xi-Fi PCIE sound card.
NEC SATA II DVD-RW
I reused a case from my old machine.  You can do that as well as long as it is a standard PC case and not a proprietary brand name case.
I have a nice Viewsonic 22" widescreen monitor.

Now I built my own machine as I usually recommend others do.  It only takes a few hours to get it put together and have the OS installed.  I have seen many people fall for some sales pitch and grab a "Bargain" machine, only to find out weeks or months later that they didn't get such a bargain after all.  If you can't build your own or don't want to try and learn it, then go to a custom PC shop in your area, or get one built online.

I got all of the above parts for about $1076.00.  Its a little more than you plan on spending on the Dell but it's worth the extra bit to same money and hassle in the future.  I got my parts mostly at Newegg.com and Ebay.  If you use Ebay, make to check out the Seller's Feedback.  i hope this helps.  I hate to see people fall into the name brand trap.  Remember anything over 4GB of RAM and you have to use a 64Bit OS, either XP or Vista. Otherwise you are wasting money and don't let some sales guy tell you different.  There is no work around to this, it's simply the limit of memory which is accessable by ANY 32Bit OS.