Help! my parents wont let me get a ps3 with my own money!??!?

OK so im 15 and im gonna be 16 this year...2 months ago i spoke with my parents about getting a ps3 and they said no... back then i didint have any money.. so i saved up and i got enough to buy the ps3 console which i plan to get for christmas.. however i dont wanna tell them bout anything coz im afraid thell say no again and then theyll be on the lookout for a ps3 console in the house.. i think they forgot about it now... you think i should go and buy it without telling them??? and if they findout somehow what shall i tell them?? Helpp plzzz