I've went from a CAAD9 to a Roubaix several years later. The CAAD9 (last of the Made in USA generation) was $2000 and the Roubaix was $4500. Speed wise they feel exactly the same, except for descending which the CAAD excels at. I've ridden centuries on the CAAD and the benefit of the Roubaix is crystal clear in this department. Saying the CAAD is "just as comfortable" is the complete opposite of what it really is - it's meant to be fast and snappy.

If you want to stick to aluminum and ride centuries, consider something like a Synapse instead. I would still go carbon and never look back. Carbon tech is now very mature (2 decades in bike applications). Contrary to certain sensationalist cycling journalism, where carbon breaks just by staring at it, you're unlikely to run into issues short of a high speed crash down Diablo.

As for the bike rack, get a new one. Top tube racks can damage any bike, not just carbon.