Advice on first ever ICE upgrade

Hi all.

I'm thinking of upgrading my current standard audio system in my Fabia VRS. I want to upgrade the speaker system, add a flat bass box in the boot, Amp, and connect it all to my new 'In Phaze' head unit. problem is, i've never done anything like this before so need some pointers or principles to follow.

I understand the speaker replacement is tricky, so i need to find someone who will fit the whole lot but i'll buy everything ready. I'm not looking for a particularly powerful set up, my aim is to have a quality full range sound thats clear and not over bassy.

Questions i have are:

- What amp do i need and with how many channels?

- Is it better to keep tweeters and mid range completely seperate rather than get combo speakers? (and then disable the tweeters)

- What are people's opinion of the flat bass boxes? Any recommendations?

Are there any other considerations i need to take into account??