1) firstly, the stock HU will never give you the kind of quality music you are looking for, even with the best speakers.
2) I would advice you to go for component speakers in the front for better quality sound. Good brands in your budget are JBL, Illusion, Ground Zero, Kicker, Polk & Auditor.
3) For rear you can opt for co-axials.
4) If at all you are installing comps in front, it will need an amp, atleast a 2 channel amp.
5) I would suggest you go for a 4 channel amp so that it can power both your comps & your sub, which you may buy later. IMO, the best budget amps is from JBL. If you want some high end amps (which are not necessary for such speakers), you can opt for alpine, blaupunkt, rockford fosgate, etc.
right now, in 10k, i would ask you to buy-
1) front comps : 4-6k
2) 4 channel amp : 4-6k
Right now, let the rear speakers be. in you next upgrade, you can change the rear speakers & add a sub. save another 10k for that.
Dont forget wiring & installation cost. dont compromise on wiring, insist on branded wiring like JBL, Earthquake, Monster cables, Scosche, etc. Install a good quality fuse.
If after all this, you are not satisfied with the thump of the sub or the sound, you may need to change your HU!