People worry far too much about the weight of a given bike, when it usually doesn't matter that much. The only times when an extra 6 pounds of bike weight matters is when you're:
- Climbing
- Hanging on with the fast folks
- Climbing
Did I mention that the extra weight will suck the life from your soul when you face a route with a lot of climbing?
Instead of bike weight... most people would be better off worrying about the component quality of the bike's spinning parts. In other words, get the best quality hubs, bottom bracket, and pedals that you can afford. Cheap or poorly adjusted bearings will slow you down waaaay more than an extra 6 pounds of bicycle will. And if you're not going to carry a heavy load, I'd go with pretty light weight rims too... they'll make the bike feel more snappy and responsive.