I am planning to buy a tablet to use it as carPC in my car. There are lot a advantage to use tablet as Carpc, it saves lots of wiring and it can be used as tablet when we are not using it in car. My main usage is GPS while driving, music, video, movies, internet. So below is my requirement.

It should have GPS mainly A-GPS as i google maps require internet and it was not available at every place here.
3G with Edge support(Mainly use it at house where i get 3G.
If it comes with android then it should have atleast android 2.1, so can update to Froyo when available.
RAM should be above 512Mb, HDMI is not main priority. Should have good sound output quality.

I have another concern about sound output, all tablet have 3.5mm jack sound output, so is it possible to use this output with basic car sound setup. I heard that ohms of such devices are low, so we wont get loud sound with car sound. Is it possbile to use these devices with car amplifier to improve sound quality.
Any forum member who have experience with tablets carPC please share your experince and thought about this. Please suggest such tablet which can be used as CarPC. Thanks in advance.