I managed to build a 3570k, and GTX670 for £940 about 2 months ago, you can do a lot better than a GT630, you will be sorely dissappointed.
right now scan.co.uk have gtx480's for £100, which is an awesome price.
but you will lose about £100 in budget terms for it being built for you. So £800 pre-built will buy you £700 of kit.
Oh and £1000 on a laptop would be a waste, as it'll be outdated much quicker than a £800 desktop, and you can never update it, so you'll have to buy again rather than update it.