Erm, choose wisely and we can only give opinions, different ppl got different opinion, we cant really choose for you, in the end, its your choice on which console you should take...
Well if you asked me, at first you need to ask yourself, how old are you?
Are you working? Since you say can attach inside your car, you must be an adult? Or still a student? Well if you're working, you don't really have time to play on your PSP, most of your time will be resting at home or hanging out with friends/gf...
If you are planning to get a PSP @ RM800.. Why not get PS3 instead?
Just ask yourself first, do you need a PSP? Will you play it often?
I agree with Soul-X. Choose wisely and what likely which games you're aiming to be playing coz DS and PSP games are....different.
If PSP preferrably PSP 3k coz go has a smaller screen and not sure if it has a car kit yet.