Dude, you're getting a Dell. Yat(somewhat). Nice specs. You have the video card as me and if BF1942 is the only game you play, your card is gonna be awesome. Ask me if you want to tweak it like overclock or increase fan speeds.
Y no OS? If you want a bit more of multimedia things, get the Dell Enhanced Keyboard and another mouse. Trust me on that. Good speakers, but maybe think about upgrading sound card to a X-FI xtremeMusic. With monitors, we now go into the whole debate of widescreen vs. regular. I have a dell 20 inch widescreen which is great for me, but does have horrible response time. You can never have too much hard drive space. But for a gamer and if your looking down the road, try to see your other video card options.
Now if your filthy rich, y not go for this model XPS 710 H2C. About $5000, but dual SLI GeForce 880GTX's, overclocked Core 2 Duo Extreme edition, 4 gigs ram, xtrememusic sound card, plus other great stuff. I think its also liquid cooled.
Anyways great computer you are thinking of getting there. I myself own the XPS 600. For $3300, other people here will say to build your own and get even better stuff, and I'm going to have to agree with them. But it's your decision so I respect that. Dam Kat, now I'm jealous.