The car details world is dangerous... I think you need to elaborate on exactly what your looking for, interior, exterior, dashboard, wheels, glass etc? Also budget... there are some nano coatings that come in a small vial at $250/vial and it hold enough to coat 4 wheels and it's empty... which is arguably better than anything that give multiple applications at $30.
Audio: JVC KD-ABT22 / JL sub+speakers / Sound deadening
Engine: WR-SRI / RRM 25% UDP / 6G75 TB
Other: RA Mudflaps