I rode on a bike with Sora for 2.5 years. This bike took me through numerous metric centuries, 100 miles most weekends, one imperial century and two MS150's (actually 180 in two days) in a hilly area of Texas. While you will find a lot of snobbery towards Sora, with tune ups it can serve you well. I put over 4,000 miles on the drivetrain and only changed tires and chains. She was still shifting well when I upgraded.

You could upgrade but Bike4Ever is honest- it would cost a lot. IMO ride the heavier bike to get stronger, learn bike handling and figure out what you like then buy a whole new bike. My much lighter bike really didn't make me much faster (maybe .5 mph), it was training and riding.

Why do you want to upgrade? Does the bike not fit?