I'm planning on buying this iMac and i already have a TV with VGA input. Do i need the 'Apple Mini DVI to VGA Adapter'. I ask this because i have read reviews saying make sure the cable you purchase is ok with your system, as there are many. Also in the picture the cable looks rather short, do i need an extention of some sort, id like to run both my monitor and tv together. If someone knows the answer please share with me, cheers