Well if you're going to have a battle royale at home on costs vs. performance, then it's definitely the Si or the 3. A Cobalt SS or a Golf GTi might mean big bills down the road, though I expect the big ecotec to be relatively robust.
Or you could go totally left field and pick up a secondhand Altima SE. Some of my previous boardmates have been cutting sub-6 0-60 times in those...