Hmm, no budget on the seps? As a start, I would recommend the Cadence ZRS-6K due to its high sensitivity rating and excellent performance for LnC. This retails around the 6,000php. For sets more than that, you should start looking for raw drivers from Cadence, Beyma, and Ciare (by order of their average price tags).

For the head unit, it's up to you. Many will opt for a 2-DIN head unit from Pioneer such as the 4250/4350 and that would also be nice. If you're focusing more on the sound quality aspect, you might want to check secondhand units of Alpine 9887s which sells around the 10k region secondhand.

For the subwoofer, it really depends on your tastes. How loud do you want it to be? If you're looking of it more from the SPL side, you would focus on this. I would suggest you start with a 15" subwoofer from RE and get the biggest sized box you can find. If space is a premium on your car, going SPL is a bit impossible now so focus on the SQL/LnC aspect.

For the amplifier, you would only need two. A 4-channel and a mono amplifier. For the mono amplifier, you have more freedom on this really. I've heard a Sound Magus mono amp drive a monster 18" subwoofer to deafening levels. However, I would suggest the DC 120.4 and their mono amplifier. Very good amplifiers and you also have brand gravitas to go along with it.

For the sound deadening, you'll eventually know the cost of it once you start playing. Allocate around 5,000php for it since you'll be doing more than deadening the doors. I'm pretty sure your license plate at the back and some windows would start rattling due to the pressure level.