actually I am not that type of person who says " yay, I beat my record, now I jumped an inch bigger!" I just like to enjoy things, like casually. there is the other side of me, but that is the geek "I need 3 monitors" part.
As I said, I would go more on reliability rather than lightweight ( my current bike is 10 kg and it is very light for me), what would be better: buy a brand new one, and use it in stock/small modification for a while, or get/built one and go with better parts? I would go with around 600 pounds, so it would be a new one with pads and postage, or go with a 300 hundred used one, change loads of bits?