The stock HU needs replaced, not amplified. It's music reproduction clarity is very sub par. An amp will only let this be made more apparent. Replace your stock speakers with quality speakers, also. Many aftermarket radios don't need an aftermarket amp unless your really like your music loud. A good subwoofer will enhance the bass feel, but I would prioritize as speakers first, HU second, amp third, subwoofer fourth, only if the HU isn't amplified enough.