When buying a new computer you basically have two options: you can either buy pre-built or you can build one yourself. In general the latter will almost always result in better value, performance, and upgradeability. If you need something that works out of the box, or are simply looking for something to recommend to your less DIY-inclined friends, then this is for you.
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips