Hi guys - I am quite keen on buying the 15 in Mac Book Pro, but I am a bit concerned about the GHz - it's only 2.2GHz, compared to the 13 in which starts at 2.7GHz. How much importance would you give GHz? To give you an idea of what I would use the laptop for - Photoshop, Light Room, MS Word - meaning, lots of programmes open simultaneously as I do a lot of heavy lifting of photos (I am a food photographer and writer, which is why I would have MS Word open on the laptop, too). Speed is very important to me, so 16GB of memory is a must. But what about GHz? Isn't 2.2GHz too low? I would have to pay a large chunk to upgrade to the 2.8GHz. There is also the option of the 2.5GHz, which is less pricey. Would love advice, please! Thank you.