ebay - i bought mine off there
dont overload the PSU though as they arent very good ones usually, but thses are £50 ish for a realy good one!
BUT! {i learnt the hard way!} dont add neons and fans etc... with a crappy PSU as you fry your mother board, PSU and processor costing you lots!
if you find cheap monitors please PM me with the address! thanks!