Pushing + cheap film = not going to happen unless you like big grain (we'll ignore Asha's results from Vista Plus for now).
The 'premium' ISO400 films are superb, have an excellent reputation, are easy to load on developing spirals, and give proven results. The cheaper ones don't have a bad reputation, and some of the Fomapan films do give a nice look, but the cost difference is relatively little.
I realised what I was paying extra for in medium format especially - the emulsion is much thicker with the better films.