speaker set up is mostly preference, with timing being the beiggest issue with placement. But as long as your speakers are placed at least somewhat close to equi-distant from your head as reasonably possible, timing issues can be corrected later.

example: i like being surrounded by my music. I like to wear it. However my hatch back poses a big problem, the front speakers are at the bottom of the front doors, but the rear speakers are maybe 12" from the back of my head. The rear speakers are waaaay too close. only fix was to move the rear speakers to custom location further back in the hatch. then use timing correction to fix the rest.