Mid-fi Car Audio: Where to start, how to go about?

Hello All you buddies..
Here is yet another requirement I need you help for.
Two of my friends have bought new cars and they expect me to select their Car-Audio components and also get it installed the right manner through a reliable guy.
Now frankly speaking, I am a total noob in this matter.

I need your help buddies.

The budget is around 60-100k for 'A' and around 100-200k for 'B'.

Basically one is looking at mid-fi while the other is looking at upper end midfi (say hifi).

Now pleeeeeeeeese share your knowledge. Here are some of the basic questions I would like to ask:

1. How to start or Where to start ?
2. What are the new age configurations that we have today (how many speakers and in which areas of the car)
3. What are the brands to be considered for wach of the components (speakers, sub, amp, head-unit, cables)
4. What could be the ratio of expenditure on each of these ?
5. Where in India are these brands/models available ?
6. Any reliable guy in Bangalore who can do the installation for me.
7. Things to remember while going about this project.

Thanks in advance guys.