I'm fairly new to cycling and just recently (about 6 months ago) bought a Specialized Allez Sport ($800) and I have how many types of different upgrades there are for bikes. And they all range anywhere from a couple hundred to a couple thousand. Obviously I'm not going to buy a crank for a couple thousand for my bike that isn't even worth a thousand. So how much would be the limit I should set on upgrades before I decide to buy a new bike? Or how do I know what the limit would be to spend on certain parts like a crank or rims or new gears, that are the more expensive parts.