Just a heads up that Dell are, as the title above says, currently refreshing their model range seemingly across the board. Changes are generally limited to CPU improvements, slightly modified cases, more up to date chipsets (seemingly 965G to G45s) , but in systems where dedicated nVidia GPUs are an optional upgrade, Dell will soon be selling 9x00 rather than 8x00 GPUs, which means performance increases in the order of 40%-80% depending on what you're running. This is great for gamers or anyone with a taste for Photoshop CS4 or anything that asks for a decent videocard. If you're a girl, yes, this does include The Sims.
Dell America is apparently running a couple of months ahead of Dell UK, so for a preview of your desired model, have a look at Dell.com . Anything that says "Big saving" probably hasn't been updated for Dell US yet either, so hold on a little longer.
Also, it's worth adding that Windows7 has been confirmed for October 22nd. No-one's announced free Win7 upgrade vouchers yet, but that will happen within the next few weeks, so again, hold on.
And by the way, before anyone pulls the "Uh lol, but if youw ait another week, there's always something better" card, there just isn't. Dell refresh their range once every 18 or so months it seems, and I reckon you're much better, in longevity terms, buying a system at the start of its cycle than the end. But it's all up to you anyway, and this is just aheads up.