What next guitar or amp?

been playing about a year and a half, now iv'e been using a strat starter pack guitar, a fender x-15. i play alot of metal/core like as i lay dying or bullet for my valentine. and im perfectly capable of playing it, but it just doesn't sound right, nothing i play sounds really like and the sound im trying to achieve, and know im playing it right. should i go with a new amp or guitar? if so any suggestions? try to keep it under $500 though.