2001 S4- The only one I'd add bolt ons to
http://www.autotrader.com/fyc/vdp.js...000&cardist=11

Then theres also your 2003-2005 Honda Accords and Nissan Altimas. I don't think you'd want to add any bolt ons to this, but I do know that they will be pretty reliable and have lots of interior room

Another option would be the newer Subaru Legacy. I don't know much about them, but their not as common as the accord and altima, should have more interior room than a wrx, and they look nice
http://www.autotrader.com/fyc/vdp.js...000&cardist=10