My car's sound

Well i have an second hand car which is really stock or all original like what you can get at the factory or car dealer.

The car that we bought have an slight defective speakers which it have a sound but can't produce more bass due to the rubber between the housing and the inner part of speaker are busted or gone, well it almost 10 yrs old and due to heat and stock due to unused the rubber is destroyed.

I change my speaker to an 6 1/2 CROWN woofer that can produce 100w-200w max with an impedance of 8ohms and also have a big magnet. which are really different from my stock speaker that can produce 15W with an impedance of 6ohms. due to financial capacity i cant afford for a better performance speaker like PIONEER, SONY, JVC, JBL, ROCKPORT, and other leading brands of speakers.

Now we mounted it at the back of my car where my old speaker are mounted but the problem is the size speaker and the size of the mounted are not the same. We make a new plan to reinsert the new speaker where the old speaker are mounted. Due to hanging and not to secure placement of speaker i experience too much vibration, then i decide to have a new board at the back of the car or be fabricated to the back of my car so that the vibration would be lessen and it can enhance the sounds system. It become more louder that the stock back boarding can't perform a good quality of sounds and speaker.