www.edmunds.com We regret to inform you that the era of the V8-powered midsize luxury sport sedan could be over. Gas prices aren’t the problem; instead, it’s the impending federal fuel-economy standards that could spell the end of these luxurious street sleepers. So this meeting of the 2008 Audi A6 4.2, 2008 BMW 550i, 2009 Jaguar [...]