1999 Mustang stereo upgrade

i want to upgrade the stereo system in my 1999 stang vert but not sure what is the right way to go i kinda want to keep the stock cd player, by the way i dont have the mach system, i was thinking of an alpine amp and infinity speakers would this be the way to go or should i just splurge and change the cd player for a new one and what would be a decent cd player? the stock system just doesnt have enough power when cruising down the highway, any suggestions would be great i also don`t want to put a sub