Pay attention to the geometry. The Roubaix has a tall head tube that make it easy to produce a tall bar height. If you need that, most of your proposed frames may create a fit problem or a dorky looking stem/spacer setup. I'd figure that out FIRST. If you can get the bike setup to fit, then give it consideration.

When you move into the $5K range I would never buy a prebuilt bike. I'd build one from scratch and get the exact components that I wanted (including Campy 11 speed).

Rather than a LOOK 586, consider a leftover LOOK 585 Ultra frame for $2200. IMO, $4K for a 586 is too much, although you might find a leftover 586 for $3K.