When people ask what to upgrade first, I usually recommend an aftermarket radio. Here’s a great article from Crutchfield Labs showing what difference aftermarket parts make for sound quality and overall loudness in an F150.
If you are looking for a low cost set of decent components, definitely add these to your list. For the price, they are great. They deliver decent low end performance, and the big silk dome tweeters deliver natural sounding highs with a relatively low crossover point.