Hey!
I hope you??re concepts are a bit clear now. As promised my line of thought for your ICE.
IMO the head unit is one of the most crucial parts of ICE. I??m not sure how the Nippon unit sounds but it certainly won??t be a good one. If you decide to change your head unit I feel fitting it with brackets won??t be a problem but you??ll loose the control for your steering wheel as I??m not sure mod??s for it are available at the moment, also you??ll loose out on the flush mount looks. So you??ll have to decide on to retain it or change it. On your inability to play certain disc??s it??s best checked with the installer as they??ll be able to give you a right answer.
You can decide on the head unit latter if you feel you don??t enjoy the sound.
For the spk??s, if I have my facts correct the spk in your car will be placed on the door??s & fire around your knees.
IMO if you go fro a woofer in your boot, you must go for the components spk (i.e. separate tweeter+ mid bass+ crossover) & a coaxial on the rear door. The reason being, you??ll already get good imaging from the fronts, thus you??ll not need another pair of components in the rear or else the tweeter placed out side will start sounding shiny.
If you don not wish to go for a woofer than I guess you must get a good 6x9 on the rear parcel tray.
I??ve heard great sounding set ups wherein they have a woofer & just a pair of front components, but I??m not sure if it would work in your budget as the set up's were quite exp.
For the amp if you go for 2 sets of spk + woofer than I feel you??ll need a 5 ch amp or 4CH + mono amp.
You can also feed the fronts & woofer from a 4 ch amp & run the rear spk through your head unit.
As for as damping is concerned I feel some installers over do it & over damp the car as if they are installing for a spl contest. The damping has to done acc to the car, type of sound required etc. So pl ask the installer as how & why he??d like to damp your car.
I hope I??ve been able to give you a brief idea. You must talk to a few installers & get a more clarity on your install vis-à-vis brands, solutions, price etc.
Some good installers in mumbai that I know of are:
Ajay Kamat (9320447654),
Pankaj Cheda of FM drive at Santacruz/Khar (98201012333),
Boom also at khar (Don??t have contact details),
Vicky of Sound FX at Andheri E (9821137909).
Let me know if can help you any further
All the best.
Cheers