Don't even think about subs when looking at the 1400 bakkie. The cabin is too small and will not give deep sound. I saw this here in Bloem once.
Rather concentrate on sound quility.
Some nice speaker enclosures in the front with a bit of fiber glass work.Look at boofheads pictures.He made some nice angled stuff for his sedan. I would reccomend that. With good planning and building you can get good sound quility.