btw, these requirements which hydra mentions may need to be changed depending on car, for e.g. if the booted variety is something you want to reclaim with

.
As per point number 3 it's not necessary that the amp is required only for high volumes. Even at low volumes it will sound much better as the amp will be able to provide more current to properly drive the speakers. The volume can be low but the clarity across all the frequencies will be better. Especially since in your case you dont plan for a rear fill. The small price difference of a 4channel amp over 2 channel is worth it. I'm repenting with a 2 channel one now. Also components like the CS2165
C are 4 speakers 2 woofs and 2 tweets with a cossover.
I kind of like the bass tube when there's fast bass like what you mention i.e. reverberating. like in trance/techno.
A ported box spreads the bass out i feel in my opinion.
Sealed is the best but then you will need more power like from a separate monoblock amp to drive that.
Do give both these setups tube/ported box a good listen with the type of music you listen to.
You can setup the filters in the amp to get low sub freq to the sub and the higher frequencies to the components. The crossover will then split up the frequencies further to the components.