Power meters: start with left only? So, another power meter question. After half a year on the smart trainer, I understand the power behind training with power. So I want a power meter. But I don't want to shell out 600 for a double sided one immediately... But I don't want just single sided power because of imbalance. This brings me to a dilemma. 

Spend almost as much money as my bike is worth for a double sided power meter? Or buy a left arm first and upgrade later.