Ride your bike and all with become clear to you with regards to why....
+1 on upgraditis. I worked in a shop for a long time while finishing school and almost without fail the person who was really interested in cycling and wasn't just looking for a beater commuter was usually back within 6 months to a year to buy something new for or completely replace the "cheap" (750$) bikes they had purchased. So if you know you are the kind of person who likes the good stuff, and you can swing it, get the most bike you can afford. If not, get something you like, ride the hell out of it, and save your nickels and dimes for the next one and relegate the old bike for "rainy days".