Here are the specs on the aspect 45
http://www.rei.com/product/780962
Here is the 55
http://www.rei.com/product/780963
and the 50
https://shop.sunrisecyclery.com/item/41336/
this should show the upgrades on the 45... the problem is finding one in a large size... I have found a couple online for about $575 to $600 but heard scott doesn't warranty bikes sold online? The local shop where I am said they could do the 50 for around $470 out the door. or they would pull the components off a 45 that they had in a different size and put it on the 50 for about $750 out the door... thats the rims, hydralic brakes, crank set, etc...