I'd say look for a closeout on a VW Passat. Or, if he want's to go small, I know the dealers around here are offerning as low as 3.9% financing on the Jettas.
He won't be able to get much in the way of an A4 for 25,000. Invoice alone is 24,600. Best way to buy an A4 is 2-3 years old at 2/3 of the original price.