If your going to do it I would say go big or go home. If your wanting something more conservative but a little more power I would say 3500, that way kinda keeping true to the alero but still get the little upgrades the 3500 has over the 3400. If your just wanting good gas mileage and a motor that will last forever, ecotec 2.2.
Put an LS2 with a 6sp in there
good reliable v8, 400 horse stock and plenty or aftermarket options.