AV advice for 2002

Hey all and Happy New Year! Im getting fed up with the poor sound in my C4S with Bose. One of the door speakers rattles, there seems to be nothing from the sub and overall it�s just crap. I�m not after a 1,000w install, just something better than what�s there at the moment with a bit of punch when highway cruising. I.e. to drown out any rattles! looking around, I�ve seen the Alpine Class D amps. For example there�s the S-A55V, which is a 5 channel amp, 4*40w and 1*100 for the sub. It works with 2ohm speakers and also high and low power signals. I�ve already got a Aliexpress head unit installed (the PO had installed a Kenwood double din unit that sucked). My plan is that amp, RCA connections to the HU and amp as that�s got 5 channel output, use factory wiring for the speakers and power. If my door speaker is blown, I�ll replace both of those too. Before I pull anything apart, any advice? For example, I can have the doors and sub each on their own channel, so not wired in parallel. Good idea or no? My thinking is I can tune them better this way and as the amp detects and copes with 2ohm speakers, I should be ok. Finally, I was looking for the factory Bose amp and found this. Is that it or do I need to dig deeper? Other installs seem to have the amps mounted vertically in front of the fuel tank.

I'm not an expert at this, but I think the Bose system mounted vertically in front are for the rear wheel drive, not the 4. Mine is that way.

Thanks. If that’s the case this has to be the smallest amp I’ve ever seen! Definitely time for a replacement, I’ll need to work out how to mount something a little bigger in its place. Any other thoughts?

Just found this article on CAI that shows how the Bose subs should be wired with an aftermarket amp. They’ve also got an article on how their setup is wired too. I’m uk based so I won’t be ordering them, sadly, the information is really useful though.