I have a 40inch sony lcd monitor it does not have a built in tv tuner, i curently use dish network so i dont need a tuner. However soon i will be going off to college and all the have there is cable (the kind without the box.) the tv has every kind of hook up but coax. so i need some kind of external tuner if possible. Is external tuner going to affect pic quality? would it be better to just buy a new tv?