| I build all my own, and have done for years, I also build machines for local SME's as has been said it's pretty easy these days, and it will work out more expensive initially, but as you upgrade you'll start to get some return as you're only replacing the components that need changing, whereas with something like a Dell desktop you'll end up swapping the lot.
And as RedSPS has said, don't skimp on quality parts, because the cheapest will be the weakest link, for example I've just upgraded my video card for the latest and next generation of games, and that cost me nearly £300 trade! | 
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