I replaced the HU in my 08 ascent hatch for a 1 din pioneer ,can't remember the serial number my stock speakers sounded fine with it they prob sounded a lil better than what they did with the factory unit. As far as the gap left the guy that installed mine put what's known as a pocket its pretty much a shelf . I got my HU installed at campbelltown JBHIFI and I got my sub installed at car audio excellence in campbelltown.both places were cheap on install paid 60 for the HU installed and 50 for the sub and amp installed