my advice would be to keep your current monitor keyboard and mouse and put your own new tower unit together yourself if u know anyone capable of putting a pc together and installing windows xp
nearly all pc's at pc world and dell brag about their graphics chips but what they dont tell you openly is that it shares teh memory that is used to run your pc so it slows down the pc's performnce dramaticly
www.scan.co.uk
they can also build systems to your reuirements and budget and will be better than anything you will ever buy at pc world or dell ( just mention you dont want onboard graphics and ask for a cheap 3d card)