I'd go for one of these:
http://www.overclockers.co.uk/showp...MD Athlon X2 5200+ 2.60GHz SILENT DDR2 System
At £234, pretty cheap, although you didn't say whether you needed an OS.
http://www.overclockers.co.uk/showp...MD Athlon X2 5200+ 2.60GHz SILENT DDR2 System
At £234, pretty cheap, although you didn't say whether you needed an OS.