I am not sure I would want to upgrade to a 570cc either. The bike is a thumper, designed to go slow, I would not want to change that.
My personal opinion is that the 570 is going to prove to be more cc's than is practical or reliable. Once the young guys here come around to my way of thinking when they are walking home after destroying the bike we will most likely start on a something more practical like a 535. On the other hand I suppose the possibility exists that they are right and I am old
My biggest worry is heat. The tranny is plenty strong enough for more HP ( I know this from factory testing). time will tell. Vibration is also a concern.
The best way for me to improve performance on my Electra X would be for me to shed 20 pounds!