I think it'll sound just fine. And if you install it yourself(I know, I know...it should be pretty easy in your car though) you won't pay anything and it'll give you something to be proud of! Probably also worth mentioning that for $50 you won't be getting a CD player. But that doesn't even matter because it's not 2002 anymore.
If you're not planning on selling your car anytime soon...just install the stereo. I don't even know how you made it this long. Or maybe just getting rid of your iPhone would be easier. I have a razr I could sell you super cheap.