No, you're being completely ripped off.
All that HDD and it's a 7200rpm? Why skimp on that? You can get 10krpm which will slash your loading times, most important if you're "GAMING GAMING GAMING".
4GB of RAM? Hello, bottleneck! More RAM means it's harder to locate things, and 4GB of RAM is the maximum supported by XP, which is lucky seeing as you've got Vista and I'm not sure what the max it supports is.
The CD/DVD drive is nothing special.
Vista Home Premium? That's a noob OS, you'll get laughed at for that. It's like XP Home with a stupid interface, and all the hardcore gamers and computer geeks had XP Pro. I got Vista Business for free off my CompSci department, and even it's lacking in features. If you want the very best, get Ultimate. At that kind of money, it's not going to make any difference.
I think you're just being blinded by big numbers and not stopping to take a closer look at things. You'd be better off doing a homebuild if you want the very best, and I know Dell's prices are dropping but you can still get better value elsewhere.