Ok, several questions
Yes, new audio equipment comes on the market all the time but it doesn't mean you need to upgrade. A lot of the stuff is small but still packs an impact.
But again, no, its definitely not obsolete. I know guys that have had the same equipment in their car for 3 or 4 years now and it still bumps hard as hell and will compete with cars that have newer equipment. Stereo doesn't necessarily become useless, but you can get better stuff if you know what I mean.
Now, you do NOT need sound deadening. That is optional. I am pushing est. 1800 total watts and don't have it. Now, I do get rattles and shakes in the cabin however, all my bass is in the cabin through a port so although I have some fixable rattles on the inside, I get no rattle whatsoever on the outside. The rattles on the inside are pretty much door panels that have been taken off so many times that they just hang from the top [img]graemlins/
But, if you want to go with the sound deadening, it will enhance the sound a bit and depending on where you put it and how much, it can make your road noise minimal as well.
Here's kind of a two-parter. You do not have to get an amp to push the speakers and make it sound better. Hell, anything sounds better than the paper cone stocks. BUT if you want to get more full potential out of the speakers, get an amp. The stereo, as all stereos, can push out a certain amount of watts before there is distortion. Even if you can't hear the distortion, its there. An amp will take over the power and feed the speakers what they need to sound more at their potential
Here's the 2nd part: The amp will not just bolt up. You need to either get a new head unit OR get an adapter that will hook up from you stock radio to the amp. Sorry, I don't know the direct name of that adapter. I know someone on here will
Other than that, I think that covers it. LMK if you have any other questions