Hondas aren't quiet inside (or known for comfortable seats) and Nissans have iffy long-term reliability, so I think we can scratch those.
It's not going to be easy to find cars that meet your price and age limits. Possibly a Toyota Camry, Ford Fusion, or Hyundai Sonata (2007 or later). A Buick LaCrosse is an outside possibility--we don't have any reliability data on the years in question, but the comfort and quietness might be better.
Stepping down a size if you can't find a good midsize sedan in your price range, check out the Toyota Corolla, Ford Focus (2008-2011, a different design than the one you drove), and Hyundai Elantra (2007-2010).
A $6,500 European brand car does run the risk of expensive repairs, and even then you'll find few within your age / mileage limits. If you're really up for rolling the dice, Saabs have excellent seats, but the manufacturer stopped selling cars here in 2011 (which does make them more affordable). Among Saabs the 9-3 was a much more recent design than the larger 9-5.
With all of these you'll want a good test drive to check out seat comfort (especially for your wife) and quietness.