Abour to buy my first iMac soon. Being new to macs I have a question regarding memory. I will be buying a 21.5 inch iMac but am concerned that the media I have to store on it will eventually slow it down. Well when considering the model with 500gb or 1tb I wonder does it make any difference in performance. To be more clear is there any difference between having the higher memory model or getting the lower one and a separate external hard drive. Does it run better being internal than external? Sorry if my question is particularly noobish.