You would do much better with a Amp system if you could persuade yourself...
However if you really do not want, save yourself some money and do what I did for a while, decent head unit with Ipod connection (I still use now) Alpine 104bti, got bluetooth and full iphone connectivity, lots of space for upgrading in the future as well if you can be tempted to try an amp then hook up some decent Crossovers.
They involve a mid/bass speaker for the door (larger) and a smaller tweater for the dash usually both connected to a crossover box which seperates the higher frequencies to the tweeters and the rest to the mid speaker.
Alpine HU - £180
Decent Crossovers (there are loads) - £100-£200
This can all be wired to the headunit and will sound good for now but will sound MUCH MUCH better powered by an amp as I have found out recently...