Can i ask what your reasoning for not wanting to build one is?
Is it because your lazy and can't be bothered shopping around for different parts or is it because you lack the knowledge/skill to do so?
If its the latter, you really should consider it, its not at all difficult to do theres lots of websites out there that will guide you through it, it really is like putting a jigsaw puzzle together and you can't really go wrong.
Building your own PC is cheaper (and not just slightly, you could easily build a computer capable of running the latest games on medium-high for 500 quid + the monitor, keyboard etc, still would work out alot less than 1k) and you can tailor the PC to suit your exact needs. Alot of these PC's come with lots of fancy stuff that although sounds fantastic, you really do not need. If you did want to spend the full 1k you could build a far superior PC to one you could buy in a shop.
For example, a 1 terabyte hard drive. That is a stupid amount of information, there is no way that any gaming users apart from hardcore pirates/video editors/CAD users would ever need that amount of space. If you did fill that amount of space your computer would be running like a 486. It just encourages you to install a load of s**te, then leave it there, taking up space and slowing the system down. If you have a decent sized hard disk, 200 gig is more than enough for an average user, then it not only saves you money but it stops you being lazy because you will actually bother to uninstall those games you finished last year and will never play again.
Seriously, look into building your own, your shooting yourself in the foot and throwing money down the s**tter otherwise.