I recommend being patient, and watching the classifieds here, and
ebay. I was in the same boat when I bought my truck, door speakers were busted.
I wound up starting with just infinity kappa 6x8's I found on
ebay for I think 150 dollars powered by the head unit. I quickly became hungry for more. Bided my time, found a used jl audio 4-channel amp to amp them, and added a jl audio sub. I slowly built my sound system one piece at a time. If you start with something good, you can make it sound great later as you can add a good amp.
I rode around with busted speakers for weeks before I found the right speakers and could afford them. Research whatever you find mentioned at a price you can afford on here and on google if you're like me and don't know anything about the items/brands mentioned. It's what I do. I think it bugs some people, but I have close to 900$ in my sound system now, and that's my hard earned money, I"m gonna ask questions and be sure I'm spending it the best way I can.
Don't just jump on whatever you can afford now if it's not right, just because you want at least a little better. You may be driving around and listening to this radio for a while yet, and you don't wanna be stuck with less than you desire later on just because you made a hasty decision before you could afford to make a better one