I think you’d struggle.
The system six was arguably the better frame and 250-300 would get you one of those. It’s only really the red and silver/red caads that command money because of saeco
The front end of the System six including the fork was a complete departure - top tube, downtube and headtube all new, and share more in common with the Six / SuperSix than the CAADs that came before it.
Six13 was Carbon main tubes, as Howard said the ones with all 3 tubes carbon are quite rare but there are others with 1 or 2 carbon tubes. Headtubes were Alu though, system six was a full one piece carbon front end bonded onto a caad9-esque rear
I think you’d struggle.
The system six was arguably the better frame and 250-300 would get you one of those. It’s only really the red and silver/red caads that command money because of saeco